Report commissioned
by the Performance Review Commission
Report on Punctuality Drivers
at Major European Airports
Prepared by the Performance Review Unit - May 2005
BACKGROUND
This Report has been commissioned by the Performance Review Commission (PRC) and prepared by the Performance Review Unit.
The PRC was established in 1998 by the Commission of EUROCONTROL, in accordance with the ECAC Institutional Strategy (1997).
One objective in this Strategy is "to introduce strong, transparent and independent performance review and target setting to facilitate more effective management of the European ATM system, encourage mutual accountability for system performance and
provide a better basis for investment analyses and, with reference to existing practice, provide guidelines to States on economic
regulation to assist them in carrying out their responsibilities."
The PRC’s website address is http://www.eurocontrol.int/prc
NOTICE
The Performance Review Unit (PRU) has made every effort to ensure that the information and analysis contained in this document
are as accurate and complete as possible. Should you find any errors or inconsistencies we would be grateful if you could please
bring them to the PRU’s attention.
The PRU’s e-mail address is [email protected]
© Cover photo ©Werner Hennies/FMG
DOCUMENT IDENTIFICATION SHEET
DOCUMENT DESCRIPTION
Document Title
Punctuality drivers at major European airports
DOCUMENT REFERENCE:
EDITION:
EDITION DATE:
PRC
Final Report
May 2005
ABSTRACT
This report analyses the drivers of punctuality at major European airports. It addresses the following
areas:
• Air traffic scheduling and air traffic management processes;
• Measuring air transport operational performance;
• Drivers of variabiliy before push back (pre-departure delays);
• Drivers of variability after push-back; and,
• Possible action areas to reducing variability of flight operations.
Keywords
EUROCONTROL Performance Review Commission - punctuality drivers - ATFM delays - drivers of air
transport variability - air traffic scheduling - declared airport capacity - service quality at airports sustainability of arrival capacity during bad weather - measuring operational air transport performance
CONTACT:
Performance Review Unit, EUROCONTROL, 96 Rue de la Fusée, B-1130 Brussels, Belgium.
Tel: +32 2 729 3956, e-mail: [email protected] - http://www.eurocontrol.int/prc
DOCUMENT INFORMATION
TYPE
Performance Review Report
Report commissioned by the PRC
PRU Technical Note
†
;
†
STATUS
Draft
Proposed Issue
Released Issue
†
†
;
DISTRIBUTION
General Public
EUROCONTROL Organisation
Restricted
;
†
†
TABLE OF CONTENTS
1.
1.1.
1.2.
1.3.
1.4.
1.5.
2.
INTRODUCTION ............................................................................................................................ 1
Objectives and scope of the report ..................................................................................... 1
Data sources and working methods.................................................................................... 2
Definitions ........................................................................................................................... 3
Organisation of the report ................................................................................................... 3
Acknowledgements............................................................................................................. 4
AIR TRAFFIC SCHEDULING AND ATM PROCESSES ......................................................................... 5
2.1.
The role of the airport community (airport, local ATC, airlines) .......................................... 6
2.1.1. Finding the “right” airport scheduling capacity to meet air traffic demand...................... 6
2.1.2. Sustainability of airport arrival capacity during bad weather .......................................... 9
2.1.2.1.
Vulnerability of airport operations to strong winds/thunderstorms....................... 10
2.1.2.2.
Vulnerability of airport operations to reduced visibility......................................... 11
2.1.2.3.
Quality of MET products and integration of MET information.............................. 11
2.2.
The role of the airline scheduling departments................................................................. 12
2.3.
The ATM en-route community’s role in preparing/managing en-route capacity............... 14
2.4.
Day of operations: The role of ATM units in managing the arrival sequence................... 15
2.4.1. En route sequencing..................................................................................................... 15
2.4.2. Circular airborne holdings to stock arrival demand ...................................................... 16
2.4.3. Combined use of circular and linear holdings to stock and sequence arrival demand 16
2.4.4. Separations on final approach and traffic bunching ..................................................... 17
2.4.5. Use of ATFM airport regulations to protect the airport short term capacity.................. 17
3.
3.1.
3.2.
3.3.
3.4.
3.5.
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE........................................................ 19
Air transport punctuality .................................................................................................... 19
Punctuality as a measure of service quality in air transport ............................................. 20
High level framework for the analysis of air transport operational performance .............. 21
Origin of variability of flight phases ................................................................................... 23
Punctuality at major European airports............................................................................. 24
4.
DRIVERS OF VARIABILITY BEFORE PUSH-BACK (PRE-DEPARTURE DELAYS) ................................. 27
4.1.
ATFM regulations and delays ........................................................................................... 27
4.1.1. Inbound traffic affected by en-route and airport ATFM delays ..................................... 27
4.1.2. Airport ATFM delays caused by the analysed airports................................................. 28
4.1.2.1.
Decision making process when managing arrival flows at airports ..................... 29
4.1.2.2.
Causes of ATFM regulations ............................................................................... 31
4.1.2.3.
Excessive use of ATFM regulations .................................................................... 32
4.1.2.4.
Accuracy and cancellation of ATFM regulations.................................................. 35
4.1.2.5.
Performance of ATFM regulations and quality assurance................................... 36
4.2.
Airline, airport and other causes ....................................................................................... 36
4.3.
Reactionary delays ........................................................................................................... 37
5.
DRIVERS OF VARIABILITY AFTER PUSH BACK ............................................................................... 39
5.1.
Variability of flight operations: taxi times........................................................................... 39
5.2.
Variability of flight operations: airborne times ................................................................... 40
5.2.1. Variations in en-route transit times ............................................................................... 40
5.2.2. Variations in en-terminal transit times .......................................................................... 40
6.
CONCLUSIONS ........................................................................................................................... 43
7.
POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY...................................... 45
7.1.
Network issues.................................................................................................................. 46
7.1.1. Establish a better understanding of “network effects” .................................................. 46
7.1.2. Post event analysis of ATFM performance .................................................................. 46
7.1.3. Introduction of a “serve by schedule” bias.................................................................... 46
7.1.4. En-route sequencing..................................................................................................... 47
7.2.
Local airport community issues......................................................................................... 47
7.2.1. Airport capacity declaration and slot allocation ............................................................ 47
7.2.2. Collaborative Decision Making Programmes ............................................................... 48
7.2.3. Improved sustainability of airport arrival capacity during bad weather......................... 48
7.2.4. Controlling arrival flows into airports............................................................................. 48
8.
GLOSSARY ................................................................................................................................ 49
9.
REFERENCES ............................................................................................................................ 52
LIST OF TABLES
Table 2-1: Service quality criteria used for capacity declaration.......................................................... 8
Table 2-2: Standard minima radar separation on approach/same runway (miles) ............................ 11
Table 3-1: IFR movements and aircraft mix ....................................................................................... 24
LIST OF FIGURES
Figure I: Arrival capacity reductions due to bad weather in 2004 ........................................................ II
Figure II: Distribution of block times ..................................................................................................... II
Figure III: High level conceptual framework for the analysis of air transport performance ................. III
Figure IV: Variability of flight phases................................................................................................... IV
Figure V: Imbalance between demand and capacity .......................................................................... IV
Figure VI: Arrival airport ATFM delays by cause of delay ................................................................... IV
Figure VII: ATFM arrival regulations due to ATC/Aerodrome at Milan-Malpensa................................ V
Figure 1-1: Overview of the data available for analysis ....................................................................... 2
Figure 1-2: Methodology used for the analysis of variability ................................................................ 3
Figure 2-1: Air traffic scheduling and ATM planning processes in Europe .......................................... 5
Figure 2-2: Reacting to stochastic perturbations.................................................................................. 6
Figure 2-3: Relationship between scheduled runway capacity and delays ......................................... 8
Figure 2-4: Airport scheduling and reduced capacity during bad weather........................................... 9
Figure 2-5: Arrival capacity reductions due to bad weather in 2004 .................................................. 10
Figure 2-6: Variability of operations, distribution of block times and targeted punctuality ................. 12
Figure 2-7: Block times and pre-departure delays ............................................................................. 13
Figure 2-8: Distribution of block times................................................................................................ 13
Figure 2-9: Circular holdings at London Heathrow airport ................................................................. 16
Figure 2-10: Linear and circular holdings at Frankfurt airport ............................................................ 17
Figure 3-1: Evolution of air transport punctuality and underlying drivers ........................................... 19
Figure 3-2: Punctuality and air transport operations .......................................................................... 20
Figure 3-3: High-level conceptual framework for the analysis of air transport performance.............. 21
Figure 3-4: Variability of flight phases (eCoda) .................................................................................. 23
Figure 3-5: Variability of flight phases by month (eCoda) .................................................................. 24
Figure 3-6: Arrival and departure punctuality ..................................................................................... 25
Figure 3-7: Mutual influence of departure and arrival punctuality ...................................................... 26
Figure 4-1: ATFM delays affecting inbound traffic into the analysed airports .................................... 28
Figure 4-2: Evolution of traffic and arrival airport ATFM delays (2003-04) ........................................ 29
Figure 4-3: Imbalance between demand and capacity ...................................................................... 30
Figure 4-4: Selecting the most appropriate tools to balance capacity and demand .......................... 30
Figure 4-5: Arrival airport ATFM delays by cause of delay (2002-04) ............................................... 31
Figure 4-6: Breakdown of arrival ATFM regulated days in 2003 and 2004 ....................................... 32
Figure 4-7: Distribution of airport ATFM arrival delay durations in 2004 ........................................... 33
Figure 4-8: ATC/Aerodrome capacity related airport regulations at Frankfurt ................................... 34
Figure 4-9: ATC/Aerodrome capacity related airport regulations at Milan Malpensa ........................ 34
Figure 4-10: The impact of cancelled ATFM regulations on departing flights.................................... 35
Figure 4-11: Cancelled airport ATFM arrival regulations ................................................................... 35
Figure 4-12: Processes affecting air transport operations before departure ..................................... 37
Figure 4-13: Distribution of departure delay by time of day .............................................................. 38
Figure 5-1: Standard deviation of taxi times at the 11 airports (2004) ............................................... 39
Figure 5-2: Holding time into London Heathrow (September 2004) .................................................. 41
Figure 7-1: Action areas for improving air transport punctuality ........................................................ 45
Figure 7-2: Rule of ATFM priority ....................................................................................................... 47
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
INTRODUCTION
forum on 20 April 2005, at which there was
a representative cross sample of interested
parties.
1
Air transport punctuality in Europe is one
of the major concerns for the industry and a
constant source of complaints from the
passengers. Not only are unpunctual flights
a major inconvenience for the passengers,
especially when connections are missed,
but they also induce large “tactical2” and
“strategic3” costs for airlines and the airline
community as a whole. Hence, reducing air
transport delays to the minimum is of major
importance for passengers, airlines and
airports.
The Performance Review Unit gratefully
acknowledges the contributions received
from everyone concerned.
The underlying analysis was made possible
by the recent availability of punctuality data
from EUROCONTROL’s Central Office for
Delay Analysis (CODA), covering now
more than 50% of scheduled flights and by
linking this data with CFMU data.
Air transport punctuality is the “result” of a
complex
interrelated
system,
which
requires detailed study for a better
understanding
of
the
underlying
performance drivers, the costs involved, as
well as the data needed to analyse and
evaluate them.
AIR TRAFFIC SCHEDULING AND AIR
TRAFFIC PLANNING PROCESSES
The scheduling of air transport operations
is the result of three inter-related
processes:
►
Airport scheduling: (Airport
declaration and slot allocation) ;
Airline scheduling; and,
ATM en-route capacity planning.
capacity
The aim of this report, which has been
commissioned by the EUROCONTROL
Performance Review Commission (PRC),
is to improve the understanding of the
various drivers affecting air transport
punctuality, with a particular focus on ATM
related issues.
►
►
The report measures punctuality at eleven
major European airports and identifies
related performance drivers. The eleven
airports
are:
Amsterdam
Schiphol,
Barcelona, Paris Charles de Gaulle, Rome
Fiumicino, Frankfurt, London Heathrow,
Madrid, Munich, Milan Malpensa, Vienna
and Zurich.
The airport scheduling process matches
airline demand and airport capacity at
strategic level. At coordinated airports,
airport capacity is often insufficient to fulfil
airline demand during peak hours.
Therefore, airport capacity is declared and
airport slots are then allocated to airlines
according to rules laid out in EC Regulation
95/1993, amended by EC Regulation
793/2004.
Each of these independently managed
processes takes place in different phases
up to the day of operations and has its own
logic and aims.
The report was prepared and validated in
interaction with the 11 airport communities,
i.e. airport authorities, airlines and ATM at
those airports. In addition, the report’s
preliminary findings and conclusions were
discussed at a workshop held in open
1
2
3
Declared airport scheduling capacity is one
of the most important parameters of an
airport. Many different infrastructural,
political and environmental factors affect an
airport’s declared capacity. However,
arguably one of the most critical factors is
runway capacity.
Air transport punctuality is usually defined as the
proportion of flights delayed by more than 15
min. compared to published departure and
arrival times (off-block/on-block vs. scheduled
times) .
“Tactical costs of delay” are related to
disruptions in airline and airport operations of
the day. This is for example the costs for
additional fuel burn.
“Strategic costs of delay” are costs associated
with time “buffers” which are often included in
airline schedules to maintain a good punctuality
record.
There is high value in finding the “right”
runway capacity and thus in maximising the
use of scarce capacity at congested
airports.
Where runway scheduling capacity is
understated, high value is lost. Where
runway scheduling capacity is overstated,
-I-
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
excess of demand will inevitably cause
local delays which may introduce variability
and disruption in the air transport network.
80
Hourly arrival capacity
Declared peak hour arrival capacity
Consequently, the declared runway
capacity
is
a
trade-off
between
maximisation of runway utilisation under
local weather conditions and the level of
delays considered as locally acceptable.
This trade-off is agreed between the airport
operator, the airlines and the local ATC
There is a clear relationship between
declared runway capacity and the level of
delays.
70
Weighted average arrival capacity when weather regulated (2004)
60
Minimum arrival capacity when weather regulated (2004)
50
40
30
20
10
Barcelona
(BCN)
Zurich (ZRH)
Madrid
(MAD)
Milan (MXP)
Frankfurt
(FRA)
Vienna
(VIE)*
London
(LHR)
Rome (FCO)
Munich
(MUC)
Paris (CDG)
Amsterdam
(AMS)
0
* value not used for airport slot calculation
Data source: EUROCONTROL, ANSPs and Airport Authorities
Figure I: Arrival capacity reductions due to
bad weather in 2004
The main drivers of reduced weather
capacity can be grouped into three
categories:
Fixing airline demand, airport capacity and
quality of service (i.e. average delay,
punctuality) at coordinated European
airports appears to be not only important
for local airport operations but also for
overall performance of the European air
transport network. Delays resulting from
local decisions may propagate throughout
the European network, creating reactionary
delays and introducing variability in daily
operations at other airports.
►
►
►
Vulnerability of airport operations to strong
winds/thunderstorms;
Vulnerability of airport operations to
reduced
visibility
(runway
layout,
equipment, processes/ policies); and,
MET forecast quality and integration of
MET information in the ATFM/ATC decision
making process.
Airline schedules are usually based on
previously flown block times and company
punctuality targets. It appears that airline
schedules generally do not consider predeparture delays. Pre-departure delays
however introduce a significant shift in the
distribution of arrival times, as shown in
Figure II (red: block to block with predeparture delays, blue: without).
Individual airlines and airports are not in a
position to anticipate the overall network
implications of their scheduling decisions.
The impact of different scheduling
approaches on the European air transport
network is not known at this stage and
should be further analysed.
Of particular relevance is the sustainability
of arrival capacity during bad weather. As
there is generally a significant capacity gap
between good and bad weather capacity,
aircraft operators may experience long
delays and/or cancellations.
Distribution of block times with and without pre-departure delays (AMS-LHR)
Number of flights in 2004
500
450
400
350
300
250
200
150
100
50
148-150
138-139
128-129
118-119
108-109
98-99
88-89
78-79
68-69
<50
58-59
0
Figure I shows significant differences in the
magnitude of arrival capacity reductions
during bad weather at the analysed
airports.
Minutes
Distribution of actual block times
Distribution of actual block times + pre-departure delays
Figure II: Distribution of block times
ATM en-route capacity planning starts
several months before the actual day of
operation. Although it is linked with airport
and airline scheduling, it is presently
independent of it.
- II -
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
Due to the high degree of public interest, it
is in an airline’s best competitive interest to
operate flights within the commonly
accepted 15-minute punctuality window of
its published schedule times. To achieve
an acceptable level of punctuality, airlines
often include “strategic” time buffers in their
schedules in order to account for a
predictable level of delay.
From an analytical point of view, this
adjustment of schedules to compensate for
expected congestion and/or flight operation
variability makes air transport punctuality
only of limited use for the measurement of
operational air transport performance.
Punctuality is a valid indicator from a
passenger viewpoint. However, punctuality
alone is not, of itself, a sufficient indicator
to assess individual airport or ATC
performance. Instead, this report focuses
on the variability of operations when
analysing
operational
air
transport
performance.
To analyse the different drivers of variability
of
flight
operations,
a
conceptual
framework has been introduced (Figure III).
Although the framework is high level and
does not capture every individual source of
variability separately, it takes a system
perspective
and
gives
a
better
understanding of the variability of the
individual
flight
phases
and
their
importance for the daily operations
Scheduled turn
around times
Drivers of departure
Departure
variability (before push-back) punctuality
Pre-departure
delays
Turn
around
times
ATFM delay
En-route/Airport
Other
airline, airport
reactionary, etc.
Scheduled block times
incl. strategic time buffers
Drivers of block-time variability
(after push-back)
Arrival
punctuality
V a ria t io n s in T A X I-IN
tim e s
There are many factors contributing to the
punctuality of a flight, on which aircraft
operators or airports have limited or no
influence. In reality, air transport punctuality
is the “end product” of a complex
interrelated
system,
involving
many
different stakeholders of the aviation
community.
V a ria t io n s in te r m in a l
tra n s it t im e s
In this study, early arrivals (i.e. more than
15 minutes ahead of schedule) are also
examined as this can be a problem as well
for air transport operations.
The cost of one minute of buffer time for an
A320 is estimated at €49 per flight. Cutting
five minutes on average off 50% of
scheduled flights in Europe thanks to
higher predictability would be worth some
€1 000M per annum, through savings or
better use of airline and airport resources.
V a ria t io n s in
e n -ro u te tim e s
The generally accepted performance
indicator for the operational performance of
airlines and airport is “punctuality”. Air
transport punctuality is usually defined as
the proportion of flights delayed by more
than 15 minutes compared to airline
scheduled departure and arrival times.
Variability4, and hence the predictability of
flight operations, is of major importance in
airline and airport scheduling. Tightening
the distribution of arrival times allows time
buffers in block times to be reduced while
maintaining punctuality.
V a ria t io n s in T A X I- O U T
a n d h o ld in g t im e s
MEASURING AIR TRANSPORT
OPERATIONAL PERFORMANCE
Figure III: High level conceptual framework
for the analysis of air transport performance
As a first step, a distinction is made
between drivers of variability before pushback and after push-back.
Departure variability (pre-departure delay)
is mainly driven by:
►
►
►
4
- III -
ATFM (en-route/airport) delays, which are
generally experienced at the departure
airport;
delays caused by airports, airlines, ground
handlers or passengers; and,
reactionary delays from previous flights.
For this report, the standard deviation has been
used to measure variations in departure time
(departure variability), arrival time (arrival
variability) or flight segment duration (e.g. taxiout time, airborne time variability) for a given set
of flights.
Turn
around
times
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
The variability of flight phases after pushback can be further broken down into
variability in:
►
►
►
►
the time to take off (taxi-out);
the cruising phase;
the terminal airspace; and,
the taxi-in phase.
While it would be desirable to analyse the
cruising phase and the terminal airspace
separately, this was not possible in this
study due to lack of necessary data. Both
phases are grouped under “Flight times”
variability in Figure IV.
DRIVERS OF VARIABILITY BEFORE PUSHBACK (PRE-DEPARTURE DELAYS)
ATFM delays essentially occur when traffic
demand exceeds ATM capacity en-route
(en-route
ATFM
delay)
or
at
departure/arrival airports (airport ATFM
delay), if no alternative measures are
available. This may be due to overdeliveries from the network or a structural
lack of capacity, technical failures,
industrial action, staff shortages or adverse
weather (Figure V).
Use of tools to
reestablish balance
“Excess demand”
30
Standard deviation in minutes (2004)
Intra European Flights
Transatlantic Flights
25
Anticipated
demand too high
(Over-deliveries)
20
06 07 08
Available capacity
(normal conditions)
15
“Reduced capacity in adverse weather”
Declared capacity
Anticipated reduction
of available capacity
(bad weather etc.)
10
5
Early
flights
Delayed
flights
Bad weather capacity
0
Arrival time
Use of tools to
reestablish balance
Figure IV: Variability of flight phases
Once the sources of variability have been
identified, it is necessary to determine if
and to what extent they can be reduced
and/or foreseen.
1 100
1 000
900
800
700
600
500
400
300
200
100
VIE
CDG/LBG*
FCO
MAD
Weather - Wind
Weather - Other or Multiple
Others
MXP
MUC
AMS
The analysis for this study has identified that
taxi-out and taxi-in phases are an issue at some
ariports only.
BCN
Weather - Vis/Fog
* includes joint regulations with Paris Le Bourget - Data source: CFMU
Figure VI: Arrival airport ATFM delays by
cause of delay
5
2002
2003
2004
ZRH
2002
2003
2004
LHR
ATC/Aerodrome capacity
2002
2003
2004
FRA
2002
2003
2004
0
2002
2003
2004
►
Departure time variations driven by predeparture delays (i.e. airline/airport
related delay such as technical failures,
ATFM delay, reactionary delay, etc.);
Variations in the flight times (cruising
plus terminal airspace).
2002
2003
2004
►
Figure VI shows significant differences in
the amount and drivers of ATFM delays at
the analysed airports.
2002
2003
2004
The main sources of variability of flight
phases at European level appear to be:
The analysis focuses on airport arrival
ATFM regulations. These were grouped
into three categories according to
underlying causes:
► ATC/Aerodrome related ATFM delays;
► Weather-related ATFM delays; and,
► Other ATFM delays.
Minutes of ATFM airport arrival delay ('000)
The taxi-in and taxi-out phases of IntraEuropean flights can introduce a nonnegligible level of variability, but relatively
low compared to other flight phases.
However, this varies by airport and
depends clearly on local circumstances5.
Variability for transatlantic flights is
significantly different in all flight phases.
Figure V: Imbalance between demand and
capacity
2002
2003
2004
Taxi in + waiting for
gate
2002
2003
2004
Flight times (enroute + terminal)
2002
2003
2004
Taxi out + holding
2002
2003
2004
Departure time
It is noteworthy that many co-ordinated
airports in Europe regularly apply ATFM
arrival regulations due to ATC/aerodrome
capacity restrictions. These restrictions
- IV -
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
should normally be dealt with during the
airport capacity declaration process. It
seems that there is scope for improvement
in this area.
more detail. Due to the significant costs
involved, many airlines and airports have
working groups dedicated to improving and
optimising those processes. European
CDM projects play also an important role
as it strives to improve the way airlines,
airports and ATM work together at an
operational level.
Figure
VII shows
the
profile
of
ATC/Aerodrome related airport ATFM
arrival regulations for Milan Malpensa
during 2003 and 2004. Here, the
systematic use of relatively short
regulations (most of which are cancelled
before the end) nearly every day at the
same
time,
suggests
scope
for
improvement.
Most reactionary delays are the result of
long primary delays (including weather
related delays, technical failures, ATFM
delays, etc.). Due to the interconnected
nature of the air transport system, long
delays tend to propagate throughout the
network, sometimes until the end of the
same operational day.
MXP - ATFM arrival regulations due to ATC/Aerodrome capacity (2003/04)
24:00
1440
23:00
1380
2003
1320
22:00
2004
21:00
1260
1200
20:00
1140
19:00
1080
18:00
17:00
1020
The propagation of delay is an important
dynamic factor, which affects the stability of
the overall network. Further studies are
needed to understand better this issue and
its impact.
960
16:00
900
15:00
840
14:00
780
13:00
720
12:00
660
11:00
600
10:00
540
09:00
480
08:00
420
07:00
01-12-04
01-11-04
01-10-04
01-09-04
01-08-04
01-07-04
01-06-04
01-05-04
01-04-04
01-03-04
01-02-04
01-01-04
01-12-03
01-11-03
01-10-03
01-09-03
01-08-03
01-07-03
01-06-03
01-05-03
01-04-03
01-03-03
01-02-03
300
05:00
01-01-03
360
06:00
DRIVERS OF VARIABILITY
AFTER PUSH-BACK
Figure VII: ATFM arrival regulations due to
ATC/Aerodrome at Milan-Malpensa
Several factors influence the issuance of
ATFM regulations:
►
►
►
►
airport scheduling;
policy on and use of local flow management
techniques;
experience
of
ATC
supervisor/flow
manager; and,
quality of information available when the
decision has to be taken.
Currently, it is difficult to realistically
determine if an ATFM regulation was the
most appropriate solution for a specific
traffic scenario because not all relevant
data are systematically captured by the
relevant stakeholders.
Detailed post-analysis addressing both predeparture ATFM delays and terminal
holding/vectoring delays is needed to find a
sustainable balance between airborne and
ground delays, depending on airports and
circumstances. Precise information on
terminal holding/vectoring delays is needed
to this effect.
Delays caused by airports, airlines,
ground handlers or passengers are a
large contributor to the variability of
departure times and need to be analysed in
Due to the multiplicity of factors affecting
air transport operations after push-back
(weather, runway configuration, human
factors, etc.), a certain level of variability of
operations is considered to be normal.
There is a need to identify the main drivers
of variability after push-back and to
determine what can be done in order to
reduce them to a minimum.
A small variance in the taxi-out and taxi-in
phases is a natural effect, depending on
local taxi distances from stand to runway.
However, this varies by airport and needs
to be analysed on a case-by-case basis.
Variations in flight times can be broken
down into en-route and terminal transit
times. Whereas there are quite significant
variations in en-route transit times for long
haul flights (strong winds, more direct
routings during off peak times, etc.), there
is only moderate variation in en-route
transit times on intra-European flights.
Depending on traffic profiles and airport
scheduling, varying arrival times of long
haul flights can represent a real problem at
some airports, as those flows cannot be
controlled by ATFM regulations.
-V-
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
►
Airborne terminal holdings appear to vary
significantly among airports. It was not
possible to analyse this in depth, however,
as the requisite data are only published for
London airports.
CONCLUSIONS
This report is a first attempt to establish a
link between air transport, airport and Air
Traffic Management (ATM) performance. It
identifies and measures an initial set of air
transport punctuality drivers at major
European airports, seen from an ATM
perspective.
This report was prepared and validated in
interaction with the airport communities
concerned, i.e. airport authorities, airlines
and ATM at those airports. This interaction
proved to be very fruitful and hopefully
results in high added value for everyone.
In addition, the report’s preliminary findings
and conclusions were discussed at a
workshop held in open forum on 20 April
2005, at which there was a representative
cross-sample of interested parties.
The Performance Review Unit gratefully
acknowledges
the
very
valuable
contributions from all those involved.
Beyond
measuring
punctuality
and
understanding underlying delay causes, the
variability of flight operations emerged as
an important issue towards improving air
transport performance. A reduction of
variability directly translates into improved
punctuality and/or reduced costs to meet
the same punctuality target. The PRC’s
eighth
Performance
Review
Report
(PRR 8) states that compressing half of
flight schedules by five minutes would be
worth some € 1000 million per annum.
The report measures the “variability of flight
operations” globally, per airport and in the
different phases of flight. It attempts to
trace the variability in arrival delays to
variability in departure time, “time-to-takeoff” (taxi-out), flight time and taxi-in. It
identifies the following as significant drivers
of “variability of flight operations”:
►
►
Airport and airline scheduling processes;
the management of bad weather at
European airports;
►
flow management strategies into airports.
Observed cases of daily ATFM airport
arrival regulations to address predictable
excess demand at airports are a signal of
airport scheduling issues and/or inadequate
use of ATFM regulations. ATFM/ airport
quality control should monitor this issue on
an ongoing basis, with visibility for all
concerned stakeholders.
Management of long haul flights bound for
Europe.
The study also gives some clues as to the
propagation of delays from flight to flight,
and hence as to ways to improve
reactionary delays.
POSSIBLE ACTION AREAS FOR
IMPROVING AIR TRANSPORT
PUNCTUALITY
The report raises many issues, which
should be further explored with a view to
improving air transport punctuality in
Europe. During the workshop on 20 April, it
became clear that further action is needed
at local level by the individual airport
communities. Action is also needed at
European level by the EUROCONTROL
Organisation and possibly by the European
Commission.
The need for a cultural change to a more
proactive,
transparent,
no-blame
management of air transport operations
was highlighted during the workshop.
Airlines, airports and the ATC and ATFM
community need to move from an “insular
perspective” to a more general focus on
overall air transport performance. At local
level, this means that the entire airport
community should work more closely
together in order to develop a common
understanding of objectives, which includes
mutually agreed and clearly defined
measurable targets.
Data access and quality are the key to
developing a comprehensive performance
measurement framework. The CFMU and
CODA data provide essential information
for progress in analysing air transport
performance at European and at airport
level. Reporting into CODA should be
further improved for a comprehensive
coverage of scheduled flights and delay
causes, possibly under EC rules, and to
- VI -
EXECUTIVE SUMMARY
Punctuality drivers at major European airports
enable analysis from a network perspective
to be conducted.
Building on this report, key drivers of air
transport performance need to be further
analysed. Comparable indicators need to
be developed at local and network level for
continuous performance monitoring.
Broadly, the areas of action can be
grouped according to their origin (local
airport community/ network) and their
nature (strategic/tactical).
Network issues
► Establish a better understanding of
“network effects”: Despite the large
share of reactionary delay, there is
currently only a limited knowledge on
how individual airline (scheduling of
block and turn around times) or airport
strategies (airport scheduling, use of
ATFM regulations, demand capacity
ratios) affect the air transport network.
► Post
event
analysis
of
ATFM
performance: Consideration should be
given by the CFMU to extending its
procedures for the management of
critical events (e.g. bad weather) and
post-event
analysis
of
ATFM
performance, with involvement of all
concerned parties. A first important step
would be a compulsory recording of
actual demand when an ATFM
regulation is issued.
► Introduction of a “serve by schedule”
bias: In order to reduce variations
against schedule, it would be
interesting to explore to what extent a
modification of the rule of ATFM priority
could help improving overall punctuality
whilst reducing the amount of
reactionary delay, provided that safety
is maintained
► En-route sequencing: More continuous
and accurate delivery of arrival flows
from the network has the potential to
improve
flight
efficiency
and
environmental friendliness in terminal
areas and would offer the possibility to
better use airport capacity and, as a
consequence, to compress airline
schedules thanks to reduced variability
of operations.
Local airport community issues
► Airport capacity declaration and slot
allocation: There is a need to evaluate
capacity declaration processes and
airport schedules at some airports,
learning from experience elsewhere
(e.g. de-peaking during certain times of
the day). The level of visibility may
need to be improved.
► Collaborative Decision Making: CDM
should be further promoted and applied
for arrival, turn-around and departure
phase.
► Improved sustainability of airport arrival
capacity during bad weather: airport
communities should strive to minimise
the gap between declared peak arrival
capacity and actual experienced arrival
capacity due to bad weather. The
feasibility and economic viability of MLS
and time based sequencing tools
should be further explored and results
should be shared with all interested
parties.
► Controlling arrival flows into airports:
There is a need for data and
performance indicators concerning
delays in the TMA, to assess the
balance between ATFM departure
delays and TMA holding.
- VII -
- VIII -
INTRODUCTION
Punctuality drivers at major European airports
1. INTRODUCTION
Air transport punctuality6 in Europe is a major concern for the industry and a frequent
source of complaints from passengers. Not only are unpunctual flights a major
inconvenience for passengers – especially when connections are missed - they also induce
large “tactical7” and “strategic8” costs for airlines and the airline community as a whole [see
also Ref.i]. Hence, reducing air transport delays to the minimum is of major importance for
passengers, airlines and airports.
Air transport punctuality is the result of a very complex system, which requires detailed
study for a better understanding of the underlying performance drivers, the costs involved,
as well as the data needed to analyse and evaluate them.
The target audience of this report is aviation professionals who have responsibility for air
traffic management, ATM capacity, airline and airport operations, planning.
1.1.
Objectives and scope of the report
The aim of this report is to improve the understanding of the various drivers affecting air
transport punctuality with a particular focus on ATM related issues. It also formulates
recommendations for future work. It represents a first attempt to establish a link between
air transport, airport and air traffic management performance.
The report was prepared by the Performance Review Unit (PRU)9 at the request of the
Performance Review Commission (PRC) of EUROCONTROL. It was validated in
interaction with the airport communities (airlines, airport, ATM), which proved to be very
fruitful.
An initial review of ATFM delay at eight major European airports was included in the PRC’s
Seventh Performance Review Report (PRR 7) [Ref.ii]. This report deepens the analysis
and extends it to eleven airports: Amsterdam Schiphol, Barcelona, Paris Charles de Gaulle,
Rome Fiumicino, Frankfurt, London Heathrow, Madrid, Munich, Milan Malpensa, Vienna
and Zurich. These airports generated the highest ATFM delays in 2003. All of these
airports are coordinated. According to EC Regulation 95/1993 [Ref iii] , amended by EC
Regulation 793/2004 [Ref. iv], the term “coordinated airport” means any airport where, in
order to land or take-off, it is necessary for an air carrier or any other aircraft operator to
have been allocated a slot by a coordinator, with the exception of State flights, emergency
landings and humanitarian flights.
For each of these 11 airports, data for 2003 and 2004 have been collected and processed.
PRR 8 [Ref.v] contains the key findings of this present report.
This report is voluntarily limited to reviewing punctuality within existing airport capacity. It is
beyond the scope of this report to look at the requirement to expand airport capacity, e.g.
through new infrastructure such as additional runways or terminals.
6
7
8
9
Air transport punctuality is usually defined as the proportion of flights delayed by more than 15 minutes
compared to published departure and arrival times (off-block / on-block versus scheduled times) .
“Tactical costs of delay” are related to disruptions in airline and airport operations of the day. This is for
example the costs for additional fuel burn.
“Strategic costs of delay” are costs associated with time “buffers” which are often included in airline
schedules to maintain a good punctuality record.
The Performance Review Unit’s Terms of reference require it to “propose, monitor and report on ATMrelated performance parameters which could include compliance with ATM procedures, airlines slot
wastage (e.g. multiple flight planning); airlines ATM delay inducement (e.g. near simultaneous flight
scheduling for same route(s)); airports (e.g. inadequacy of airside facilities); and other related factors”
(PRU ToR, 2b).
-1-
INTRODUCTION
Punctuality drivers at major European airports
1.2.
Data sources and working methods
There are many different data sources for the analysis of operational air transport
performance. For consistency reasons, most of the data in this report were drawn from the
EUROCONTROL Central Flow Management Unit (CFMU) [Ref.vi] and the Central Office
for Delay Analysis (CODA)10. Furthermore, a variety of studies listed in the bibliography,
were used in this report.
The underlying analysis was made possible by the simultaneous availability of CFMU data
and CODA data. The continued availability and use of such data will be essential for
improving air transport network performance in Europe.
600
500
400
300
200
100
Milan
Malpensa
(MXP)
Vienna (VIE)
Zurich (ZRH)
Barcelona
(BCN)\
Rome
Fiumicino
(FCO)
Munich (MUC)
Madrid (MAD)
Amsterdam
(AMS)
London
Heathrow
(LHR)
Frankfurt
(FRA)
0
Paris Charles
de Gaulle
(CDG)
IFR departures and arrivals in 2004 ('000)
The CODA sample used in this report includes 2.7 million IFR flights in 2003 and 3.6 million
IFR flights in 2004. Overall, CODA data now covers some 50-60 % of commercial flights in
Europe. Not all aircraft operators disclose the delay cause, which is one reason for the
different coverage at each airport, as shown in Figure 1-1.
Total IFR arrivals and departures (CFMU)
CODA records with delay breakdown
CODA records without delay breakdown
Figure 1-1: Overview of the data available for analysis
With a view to encouraging an open and ongoing dialogue between all the involved parties,
a preliminary analysis combined with a questionnaire were sent to the respective airport
communities to get some initial feedback. The findings were validated by airport operators,
ANSPs and airlines. A workshop was then held on 20 April 2005 at which there was a
representative cross sample of interested parties (airlines, airports, ANS providers, national
authorities, the European Commission and EUROCONTROL).
The outcome of this workshop has been taken into account in this report.
10
The purpose of the EUROCONTROL Central Office for Delay Analysis (CODA) to provide interested
parties with timely, consistent and comprehensive information on the air traffic delay situation in Europe.
CODA data is supplied by airline operators and includes information on delay causes, based on IATA delay
codes. The data set contains the scheduled and the actual pushback times, actual take-off time, actual
landing time, and scheduled and actual gate arrival times often referred to as Out, Off, On, In (OOOI) data.
Furthermore, it contains IATA delay codes for up to five causes of delay. It should be noted that One
differencing factor between CFMU delay data (ATFM regulations) only records primary delay causes,
whereas CODA data also reports reactionary delays.
-2-
INTRODUCTION
Punctuality drivers at major European airports
1.3.
Definitions
Flight leg:
All occurrences of a scheduled flight (e.g. AF 3451) on a given origin-destination (e.g.
Brussels to Lyon).
Variability of flight operations:
Variability and predictability of flight operations are closely linked and essential factors
in airport and airline scheduling. The wider the spread of arrival times, the more difficult
it is to predict the duration of a given flight leg during the scheduling phase.
For this report, the standard deviation11 has been used to measure variations in
departure time (departure variability), arrival time (arrival variability) or flight segment
duration (e.g. taxi-out time, airborne time variability) for a given set of flights.
Mean and standard deviation were computed for the whole flight sample and for
individual flight legs (see Figure 1-2). The variability of flight times12 for a given flight leg
is called the intra-flight variability. Intra-flight variability is the relevant parameter from a
scheduling point of view and is therefore used for analyses of variability of flight
operations in this report.
Applied filters for data analysis:
Dep/Arr PCT: between -90 and 360 min.
Taxin out/in: between 1 and 90 min.
Flighttime: >15 min.
CODA
Database
Intra-flight variability
(aggregation per sub-group/ month)
Applied aggregation criteria:
Identical operator, Sched. DEP & ARR time
Origin & destination airports
> than 20 services per month
Overall variability
of flight phases
(Mean of individual
intra-flight variabilities)
Figure 1-2: Methodology used for the analysis of variability
1.4.
Organisation of the report
The report is organised as follows:
• Chapter 2 describes processes and issues involved in air transport operations. It
also shows the capacity issues at the 11 airports.
• Chapter 3 discusses the use and suitability of punctuality as performance indicators
for air transport operations and introduces a high-level framework for the analysis of
operational performance. The chapter the analyses the variability of flight phases
before looking at the arrival and departure punctuality at the 11 major European
airports.
• Chapter 4 analyses the drivers of operational variability before push back (predeparture delays) in more detail.
11
12
A statistic used as a measure of the dispersion or variation in a distribution, equal to the square root of the
arithmetic mean of the squares of the deviations from the arithmetic mean.
Sub-groups were calculated on a monthly basis. Only flights with the same parameters (operator,
scheduled departure/arrival time, origin/destination) and with a frequency of 20 or more flight per month
were included in the calculation.
-3-
INTRODUCTION
Punctuality drivers at major European airports
•
•
•
1.5.
Chapter 5 examines the drivers of operational variability after push-back.
Chapter 6 summarises the main conclusions.
Chapter 7 discusses possible areas for future work in order to reduce the variability
of air transport operations, with a particular focus on ATM related issues.
Acknowledgements
In undertaking this study, the Performance Review Unit has been assisted by a large
number of people in the aviation industry, including airports, airlines, organisations and
others. The PRU would like to thank everybody who contributed to this report for their
invaluable co-operation.
-4-
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
2. AIR TRAFFIC SCHEDULING AND ATM PROCESSES
This chapter describes the processes and issues involved in air transport operations. It also
shows the capacity issues at the 11 airports.
The scheduling of air transport operations is the result of three inter-related processes:
• airport capacity declaration and subsequent airport slot13 allocation;
• airline scheduling; and,
• planning of ATM en-route capacity for next summer/ winter season.
Each of these independently managed processes (airport community, aircraft operators
and the ATM community) takes place in different phases up to the day of operations
illustrated in Figure 2-1 and has its own logic and aims.
Airport
capacity
Parties
Involved
12 - 7 months
before season
7 - 6 months
before season
6 months to 2
months before
season
Airport community
(local ATC, airline,
airport)
Analysis of available
data to determine
airport scheduling
capacity at a given
quality of service
Airport scheduling
capacity
Declaration (incl. hourly
capacities at a given
quality of service)
IATA scheduling
conference Airport slot allocation
and adjustments /
reallocation of returned
slots
Airline
scheduling
Airline scheduling
department
En-route
capacity
ATM community
(EUROCONTROL, ANSPs)
Strategic ATFM capacity
planning (post analysis &
traffic forecast STATFOR)
Draft schedule based on
the business plan of the
airline.
Formulation of schedule
and planning of
necessary resources
(crew, aircraft, etc.) –
Publication of airline
schedule.
Strategic ATFM capacity
planning (post analysis &
traffic forecast STATFOR).
Coordination
EUROCONTROL and
ANSPs. Focus on
RNDSG, ATCOs staff
roster, RAD, EAW
Further assignments of
airport slots and minor
adjustments up to 48
hours before the day of
operations.
Minor amendments to
the schedule up to 72
hours before the day of
operation
Pre-tactical ATFM planning
1 day before
operation
Preparing for next day
of operation.
Preparing for next day of
operation
ATFM daily plan for next
day of operation
Strategic ATFM measures
Day of
operation
Day-to-day airport
operations
management
Day-to-day airline
operations management
Monitoring of available
capacity and traffic.
ATFM measures
(re-routing, level capping,
ATFM regulations).
6 days before
operation
Figure 2-1: Air traffic scheduling and ATM planning processes in Europe
13
The airport coordinator allocates available slots to aircraft operators, based on the airport declared capacity
and airline requests. Airlines have to obtain airport slots at each coordinated airport.
-5-
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
All actors share the interest to maintain safe, orderly and sustainable operations and to
improve overall network performance. However, individual interests may be competing for
the same resources: airport slots, airspace, ATC capacity. These conflicting requirements
have to be resolved by airport co-ordinators, airline conferences and ATFCM processes.
As illustrated in Figure 2-1, the process by which air traffic demand is matched to airport
scheduling capacity starts long before the actual flight takes place. Typically, several
months before the beginning of the summer/winter season14, the airport community (airport
authority, local ATC and airline representatives) determines the airport declared capacity
(see Section 2.1).
The outcome of the airport declaration process is the number of airport slots that can be
allocated to aircraft operators hourly, but also during time bands (generally 10 minutes).
Based on those allocated airport slots, aircraft operators build their commercial schedules
(see Section 2.2) and assign the necessary resources (aircraft, crew, etc.).
While the airport communities and airlines prepare their schedules, the ATM en-route
community (EUROCONTROL and ANSPs) prepares capacity plans for next summer/winter
season, with some built-in operational flexibility (see Section 2.3).
Section 2.4 examines the role of ATM units in managing the arrival sequence, which is
most relevant to the air transport performance measured in this report.
The management of arrival flows in daily operations aims to balance continuously the
actual runway capacity and the actual traffic demand. This is based on flight plans and
progressively updated by further messages and by radar information, if available. The
process of managing arrival flows may require the use of ATFM regulations depending on
the type of the ATM organisation and the excess of demand compared to available runway
capacity (see Figure 2-2).
ATFM ground
regulation
Management of
airborne arrival
flows
Scheduled
demand
Available
runway
capacity
Figure 2-2: Reacting to stochastic perturbations
2.1.
The role of the airport community (airport, local ATC, airlines)
2.1.1. Finding the “right” airport scheduling capacity to meet air traffic demand
The airport scheduling process matches airline demand and airport capacity at the strategic
level. At coordinated airports, airport capacity is often insufficient to fulfil airline demand
during peak hours.
According to EC Regulation 95/1993 [Ref.iii], amended by EC Regulation 793/2004 [Ref.iv],
the term “coordinated airport” means any airport where in order to land or take-off, it is
necessary for an air carrier or any other aircraft operator to have been allocated a slot by a
14
Air transport operations can be divided into summer season (April to October) and winter season
(November to March). For the planning of en-route capacity, the summer season is more critical due to
higher demand.
-6-
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
coordinator, with the exception of State flights, emergency landings and humanitarian
flights.
Airport scheduling at a coordinated airport is based on two distinct but interrelated local
processes. In the first step, the airport authority declares its airport scheduling capacity and
in a second step the airport slot coordinator allocates airport slots15 to airlines, according to
rules laid out in EC Regulation 95/1993, amended by EC Regulation 793/2004. These EC
rules have endorsed the IATA Worldwide Scheduling Guidelines [Ref.vii] and take into
account the principles of transparency, neutrality and non-discrimination.
The local ATC capacity (including the arrival runway throughput) should be taken into
account when determining the declared airport capacity and subsequently the airport slots
allocated to aircraft operators.
The airport capacity declaration process is generally based on analysis involving a large
amount of data. Essentially, the declared capacity of coordinated airports tries to maximise
the use of available airport capacity whilst keeping delays at locally acceptable levels. The
capacity declaration process requires an objective analysis of scenarios to accommodate
the air traffic demand, taking into account all the issues that may restrict airport capacity.
Without any doubt, declared airport scheduling capacity is one of the most important
parameters of an airport. There are different methods to determine airport declared
capacity but all approaches usually consider the following parameters:
• runway capacity under different meteorological conditions;
• terminal ATC capacity;
• apron/taxiways;
• traffic mix (wake vortex categories of aircraft);
• passenger terminals/gates;
• environmental and/or political restrictions (i.e. cap of annual movements); and,
• service quality parameters (average delay, punctuality).
One of the most critical factors of airport capacity is the runway capacity (arrival capacity in
particular). There is high value in finding the “right” runway capacity and thus in maximising
the use of scarce capacity at congested airports.
Where runway scheduling capacity is understated, high value is lost16 [for further reading
see Ref. viii]. Where runway scheduling capacity is overstated, excess of demand will
inevitably cause local delays which may introduce variability and disruption in the air
transport network. It is a trade-off between maximisation of runway utilisation under local
weather conditions (the quantity of airport slots) and the level of delays considered as
locally acceptable (i.e. the quality of airport slots). This trade-off is agreed between the
airport operator, the airlines and the local ATC (see Figure 2-3, right side).
15
16
The term “airport slot” refers to the permission given by a coordinator in accordance with EC Regulation
793/2004 to use the full range of airport infrastructure necessary to operate an air service at a coordinated
airport on a specific date and time for the purpose of landing or take-off as allocated by a coordinator.
One hourly airport slot is worth several million Euro per annum at a main European hub.
-7-
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
Theoretical runway capacity
Delay criteria
10min
Influencing factors:
• Airport layout
• Runway configuration
• Runway occupancy
• Weather
• Scheduling and traffic mix
• Separation minima
• Wake vortex separation
• Airspace and ATC procedures
• Environmental constraints
Average
delay
Quality of Airport
Slots
Declared Airport
Runway Capacity
2min
Number of Airport
Slots
Scheduling rate (mvts/ hr)
Figure 2-3: Relationship between scheduled runway capacity and delays
According to the queuing theory, airport throughput is maximised when there is a sufficient
number of aircraft ready to land during peak times. This implies that a certain level of delay
is unavoidable if runway throughput is to be maximised.
There is a clear relationship between declared runway capacity and the level of delays (see
Figure 2-3, centre). As the volume of the traffic increases, delays remain relatively low until
a certain point is reached at which delays increase disproportionately [for further reading
see Ref. ix].
An airport’s scheduled arrival capacity is usually declared at a given level of service quality
(see Table 2-1). At some airports, the service quality criterion is punctuality. At others, it is
the average arrival delay or the average holding time. There are currently no consistent
criteria to give aircraft operators an indication of the “quality” of the allocated airport slot,
neither is it possible to compare airport slot quality across airports.
Service quality criteria
Weather
considerations
AMS
average arrival delay
Normal day
BCN
FRA
punctuality (>15 min.)
punctuality (>15 min.)
LHR
average arrival delay
MAD
punctuality (>15 min.)
MXP
zero delays17
MUC
average arrival delay/
punctuality (>15 min.)
CDG
average arrival delay
FCO
zero delays18
VIE
ZRH
punctuality
punctuality (>15 min.)
Airport
Normal day
Comment
4 minutes average delay from entry of AMS FIR to
landing, based on peak arrival periods during 3 months
in the summer. Taxi times are excluded.
Scheduled arrival compared to on block time
IATA scheduled arrival compared to on block time
10 min. average target based on 6 “normal days” –
holding stack to threshold (taxi time not incl.)
Scheduled arrival compared to on block time
In accordance with CFMU parameters. No monitoring of
airborne and taxi delays.
Difference between actual and estimated time of arrival
(ETA). The ETA is calculated by adding a Standard
Approach Time. Furthermore, punctuality is monitored
by airlines and airport.
6 min. average target <2004 >
In accordance with CFMU parameters.
No monitoring of airborne and taxi delays.
Flight plan ETA vs. actual time of arrival
Scheduled arrival compared to on block time
Table 2-1: Service quality criteria used for capacity declaration
Airports also use different time bands as part of the airport slot allocation process18. The
wider the time band, the more likely is “bunching” of schedules, especially at the beginning
of each hour.The impact of this practice on punctuality has yet to be analysed in detail (see
also 2.2).
17
18
See Aeronautical Information Publication (AIP)
For example one airport might use 10 minute intervals whereas the next airport uses 30 minute intervals for
the allocation of airport slots.
-8-
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
Fixing airline demand, airport capacity and quality of service (i.e. average delay,
punctuality) at coordinated European airports appears to be not only important for local
airport operations but also for overall performance of the European air transport network.
Delays resulting from local decisions may propagate through the European network
creating reactionary delays and introducing variability in daily operations at other airports.
However, if such local delays are predictable, aircraft operators can take them into account
in their scheduling, in which case propagation throughout the network reduces.
Individual airlines and airports are not in a position to anticipate overall network implications
of their scheduling decisions. The impact of different scheduling approaches on the
European air transport network is not known at this stage and should be further analysed.
2.1.2. Sustainability of airport arrival capacity during bad weather
Optimum use of airport capacity has high value for airspace users and airports. In order to
reduce weather-related disruptions to a minimum, airports need to focus on measures that
mitigate the impact of weather.
Of particular relevance is the sustainability of arrival capacity during bad weather. As there
is generally a significant capacity gap between good and bad weather capacity, especially
when the trade-off between bad and good weather capacity has been chosen at a high
level of capacity, aircraft operators may experience long delays and/or cancellations. As
already pointed out, local delays are also likely to affect other airports in the European
network in the form of reactionary delays.
To some extent, the capacity reduction during bad weather operations is influenced by the
assumed service quality criterion (i.e. average delay of 5 or 10 minutes) that was used
during the airport capacity declaration process. For example, operations at an airport which
has factored-in a high average delay during the capacity declaration process are likely to
be affected more severely during adverse weather than operations at an airport which has
factored-in a moderate average delay.
mvts/hr
Declared capacity
(10min. avg. delay)
Declared capacity
(5min. avg. delay)
Capacity gap 1
Capacity gap 2
Available capacity
during bad weather
Duration of weather phenomenon
Figure 2-4: Airport scheduling and reduced capacity during bad weather
However, the capacity reduction during bad weather is clearly more significantly influenced
by the preparedness of the airport for bad weather (equipment and processes in place) and
by the given airport layout and relevant usage (i.e. independent or dependent parallel
runways, direction of runways).
In order to provide an overview of the main influencing factors, the following areas are
addressed in the next sections:
1. Vulnerability of airport operations to strong winds/thunderstorms;
2. Vulnerability of airport operations to reduced visibility;
o Use of dependent or independent parallel runways
o Equipment: navigational aids
o Processes: arrival separations applied on the same runway
3. MET forecast quality and integration of MET information in the ATFM/ATC decisionmaking process.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
If weather conditions are anticipated to significantly reduce the airport capacity, ATFM
airport regulations can be issued in order to limit the number of flights arriving at the airport.
The challenge is to determine accurately the period of loss of capacity and to sustain the
highest achievable runway arrival rates while maintaining safety at all times.
Figure 2-5 examines the relation between airport declared peak hour arrival capacity and
ATFM rates issued by airports when weather regulated (including all causes, i.e. strong
winds, low visibility etc.). The observed capacity gap gives a first idea of the airport’s
vulnerability to bad weather conditions.
Figure 2-5 shows significant differences in the magnitude of arrival capacity reductions
during bad weather. When affected by severe weather conditions during peak times,
airports such as Amsterdam, Paris Charles de Gaulle, Munich and Rome Fiumicino are
more likely to cause extensive local delays and some disruptions to the European network
in form of reactionary delays than airports such as Frankfurt and London Heathrow.
80
Hourly arrival capacity
Declared peak hour arrival capacity
70
Weighted average arrival capacity when weather regulated (2004)
60
Minimum arrival capacity when weather regulated (2004)
50
40
30
20
10
Barcelona
(BCN)
Zurich (ZRH)
Madrid
(MAD)
Milan (MXP)
Frankfurt
(FRA)
Vienna
(VIE)*
London
(LHR)
Rome (FCO)
Munich
(MUC)
Paris (CDG)
Amsterdam
(AMS)
0
* value not used for airport slot calculation
Data source: EUROCONTROL, ANSPs and Airport Authorities
Figure 2-5: Arrival capacity reductions due to bad weather in 200419
2.1.2.1.
Vulnerability of airport operations to strong winds/thunderstorms
Airport vulnerability to strong winds is influenced by the runway layout and the wind
directions typically experienced at the airport. For example, at one airport, strong winds
might only lead to a marginal capacity reduction whilst at another airport the need to
change from the most efficient runway configuration to a less favourable one results in a
significant capacity reduction. It should be pointed out that runway selection is not only
affected by surface winds but also by winds in the altitude band 1000-4000ft, as those
winds can severely affect aircraft on approach.
Some analysed airports consider a cross wind20 of 20 knots as the critical value which
requires a change from the optimal to a sub-optimal runway configuration (Rome
Fiumicino, Amsterdam). The use of a less optimal runway configuration often results in a
significant reduction of airport capacity (for example Rome Fiumicino) and/or an increase in
taxi times because the alternate runway is further from the terminal, as is the case at
Amsterdam airport.
19
20
The minimum arrival capacity is the average of the 5 weather related ATFM airport arrival regulations with
the lowest arrival capacities in 2004.
Gusting winds were not analysed in more detail.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
The critical value for tail wind varies from 5 to 10 knots depending on the airport in
question. If those wind conditions are reached, the runway is changed from the optimal
configuration to a less optimal configuration in order to preserve the safety of operations.
Some airports (such as Rome FCO) reduce the runway capacity due to the lack of rapid
exits serving the second best runway configuration, which increases the runway occupancy
time during strong tail wind.
Strong head winds on final approach reduce the ground speed of the aircraft and hence
increase the time between landings, thus reducing the available arrival capacity. This will
impact on any airport with high traffic intensity.
2.1.2.2.
Vulnerability of airport operations to reduced visibility
Poor visibility can severely affect airport operations. The magnitude of capacity reduction
generally depends on runway layout (e.g. parallel dependent or independent), use of
runway layout, available approach equipment and ATC/ATFM processes in place.
When an airport has dependent parallel or converging runways, arrival capacity in poor
visibility conditions can be severely reduced. When one of runway has to be closed, the
arrival capacity might be halved in extreme cases. Even if it is not necessary to close one
runway or to change runway configuration, larger separations between aircraft are applied
for safety reasons in low visibility conditions, e.g. ILS CAT III operations.
Table 2-2 shows that separations during low visibility operations vary between the analysed
airports, resulting in different arrival capacities during similar weather conditions. This might
be due to local procedures or a lack of appropriate navigational/visual aids to maintain a
high arrival flow during poor visibility. Most of the analysed airports are equipped with ILS
CAT IIIA or higher which helps to keep the capacity gap to a minimum during poor visibility.
Airport (2004)
Paris Charles de Gaulle
Frankfurt
London Heathrow
Amsterdam
Madrid Barajas
Munich
Rome Fiumicino
Barcelona
Zurich
Vienna
Milan Malpensa
ILS-CAT I
ILS-CAT II
ILS-CAT IIIA
ILS-CAT IIIB
2,5-3
2.5-3 (2)21
2.5-3
3
3
3
3-5
4
3
2.5
3
6
6
6
6
6
6
Not specified22
1623
6
5
8
6
8
6
8
6
6
Not available
1623
6
5-7
10
6
8
6
9
n/a
6
Not available
1623
6
5-7
15
Table 2-2: Standard minima radar separation on approach/same runway (miles)
London Heathrow airport is considering further reducing the capacity gap by introducing a
Microwave Landing System (MLS). MLS has advantages over ILS: it is less sensitive to
beam bends and reflected signal interference, so that separation between arriving aircraft
can be reduced to less than 6 nautical miles in all weather conditions including CAT IIIB.
2.1.2.3.
Quality of MET products and integration of MET information
The quality and the integration of MET information in the ATFM/ATC decision-making
process are clearly important in order not to waste scarce airport capacity. A wrong or
misinterpreted MET forecast could lead the ATC supervisor to constrain the arrival demand
even when this is not necessary.
It would be desirable to get a better understanding of how possible differences in the
quality of the MET information and/or insufficient integration of the information in the
21
22
23
Value in brackets for staggered operations.
Choice made by supervisor according to traffic situation and separation standards as in ICAO Doc. 4444.
10 miles if two runways are in use – 16 for single runway operation.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
decision-making processes affect bad weather operations at an airport. It would therefore
be interesting to explore the following issues in more detail:
• What is the quality of the available MET forecast?
• What are the drivers of the quality of MET products (expertise, models, technology)
• Are the most suitable MET products available to decision-makers?
• Are MET products efficiently used in the ATC/ATFM decision-making processes?
One proactive initiative to reduce weather impact on daily operations is the Capacity
Prognosis Schiphol tool (CPS). CPS is a joint project of the AMS airport community
involving LVNL (ATC), KNMI (MET-provider), KLM and the airport authority. It is the result
of an initiative to establish the probability of a capacity reduction at AMS Schiphol Airport
and to enable the respective parties to act and prepare accordingly. The key idea is to
make optimum use of available capacity by anticipating the most likely capacity scenario,
based on a tailor made weather forecast by KNMI.
2.2.
The role of the airline scheduling departments
As already pointed out in previous paragraphs, flights may suffer delays and yet be on
time, if predictable delays (variations in block-to-block times24) are catered for through “time
buffers” in flight scheduling. Extending buffers improves punctuality and hence customer
satisfaction, as illustrated in Figure 2-6, but entails high additional costs [for further reading
see Ref. i].
The “buffer” or “strategic delay” included in airline schedules depends on quality of service
targets set by the airline. The predictability of arrival times is essential information in
scheduling flights for the next season.
Nr. of flights
Median
80%
80%
Buffer 1
Buffer 2
Time
Figure 2-6: Variability of operations, distribution of block times and targeted punctuality
The calculation of the scheduled block time is usually based on the observed previously
flown block times. The schedule is set by applying a percentile target to the distribution of
previously flown block times. In the example in Figure 2-6, the punctuality target is set so
that around 80% of flights will arrive on time at the arrival airport. The wider the distribution
(and hence the higher the level of variation), the more difficult and costly it gets for airlines
to meet the punctuality target, as more “strategic” buffer is required.
Depending on the airline, the calculated block time is often used for the entire scheduling
period, for all times of the day and for all weather conditions as observed in Figure 2-7.
24
Block time is generally referred to as the time between off-block at the departure airport and on-block at the
destination airport.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
minutes
Block times (actual and scheduled) and pre-departure delays
on a typical Intra-European city pair
150
150
140
140
130
130
120
120
110
110
100
100
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Average delay before going off block (actual versus scheduled off-block)
Actual block times (average gate-to-gate)
Scheduled block times (average gate-to-gate)
Figure 2-7: Block times and pre-departure delays
Since schedules for the new season are based on previously flown block times, Figure 2-7
suggests that some airlines may not adjust their schedules to account for pre-departure
delays25, e.g. ATFM delays. In most cases, scheduled block times closely correspond to
actual average block times, resulting in a worsening of punctuality when pre-departure
delays occur.
Distribution of block times with and without pre-departure delays (AMS-LHR)
Figure 2-8 illustrates
how
pre-departure
delays affect actual
travel times between
two airports.
Number of flights in 2004
500
The blue area in
Figure 2-8 shows the
distribution of actual
flown
block-to-block
times26.
450
400
350
300
250
200
150
100
50
148-150
138-139
128-129
118-119
108-109
98-99
88-89
78-79
68-69
58-59
<50
0
Minutes
Distribution of block times with and without pre-departure delays (LHR-VIE)
300
250
200
150
100
50
Minutes
Distribution of actual block times
Distribution of actual block times + pre-departure delays
Figure 2-8: Distribution of block times
25
26
Delays which occur before push back (e.g. delay due to late boarding, ATFM delay, reactionary delay)
Duration between off-block at departure airport and on-block at the destination airport.
- 13 -
238-240
228-229
218-219
208-209
198-199
188-189
178-179
168-169
158-159
148-149
138-139
128-129
118-119
108-109
0
<100
As can be observed,
pre-departure delays
have
a
significant
influence
on
the
distribution of actual
block-to-block times,
different for each flight
leg.
Distribution of actual block times + pre-departure delays
Number of flights in 2004
The distribution of the
total
travel
times
including pre-departure
delays is represented
by the red line.
Distribution of actual block times
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
Airlines take other factors into account when scheduling services, e.g. the level of
competition, the type of operation (hub and spoke versus point to point), and the (network)
value of payload on that route. Some computer reservation systems list flights according to
scheduled travel time, which may encourage airlines to choose a shorter scheduled travel
time to gain better visibility in the reservation system.
The same holds true for airport slots. Airlines might decide to schedule a specific block time
for a flight due to the lack of a suitable pair of corresponding departure and arrival airport
slots. This may occur when the length of time band and its characteristics differ between
both airports.
2.3.
The ATM en-route community’s role in preparing/managing en-route capacity
Months in advance, ANSPs and EUROCONTROL plan the ATM capacity that will be made
available during the next summer/winter season.
This process is independent of the previously described two processes of airport and airline
scheduling. Post analyses are based on previously flown flight plan data rather than on
scheduled data. EUROCONTROL STATFOR statistics are used as traffic forecast data.
The outcome of the airport and airline scheduling processes could be available in
November and in January respectively, but they are not taken into account.
The following processes are concerted actions, which are meant to ensure that enough
ATM capacity will be made available during the next season:
1. The Future ATM Profile (FAP) simulations led by EUROCONTROL verify that the
planned en-route capacity for each European ACC is in line with the ATFM en-route
delay target of one minute. There are 2-3 iterations in order to assess the impact of
additional ACC plans, should the first simulation identify capacity gaps.
2. The Route Network Development Sub-Group (RNDSG) agrees and implements
route design changes for reducing ATC complexity and re-distributing the traffic in
high-density areas and for improving flight efficiency where possible.
3. The Airspace Utilisation Sub-Group reviews busy weekends in order to request to
the relevant military authorities timely access to weekend routes (EAW).
4. The ACCs decide on staff rostering, taking into account staff roster rules, the
forecast traffic and previous ATFM en-route delays generated by combined sectors.
5. The CFMU reviews the Route Utilisation Scheme (RAD) during the strategic phase
in order to better structure the traffic and/or to re-distribute it. This measure normally
replaces pre-tactical or tactical ATFM measures, which are frequently used.
Currently there are no practical, measurable and transparent criteria to decide when
a strategic measure is better than a pre-tactical or tactical ATFM measure.
On the day preceding actual operations, the CFMU compares the planned demand with the
available capacity. After having discussed minor capacity adjustments with ACCs, the
CFMU issues the ATFM daily plan for the next day. This plan contains all ATFM measures,
which are implemented in order to manage the network efficiently, taking into account the
demand and the available ACC and, possibly, when known in advance, airport capacities.
ATFM measures that can be used to manage the European network are:
1. Compulsory level capping;
2. Voluntary or compulsory re-routing; and,
3. ATFM regulations.
On the same day, the CFMU also issues an Airspace Use Plan (AUP), which provides the
availability of conditional routes through temporary reserved airspace.
The use of ATFM airport regulations to protect short-term airport capacity is discussed in
the next paragraph.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
2.4.
Day of operations: The role of ATM units in managing the arrival sequence
As already discussed, airport throughput is maximised when there is a sufficient number of
aircraft ready to land, during peak times. This implies that a certain level of delay is
unavoidable if runway throughput is to be maximised. However, as already seen, in this
type of situation the service quality is likely to decrease very rapidly with the increase of the
demand.
Maximising the use of runway capacity typically requires an accuracy of a few seconds in
delivering aircraft at the final approach fix. Saving 5/6 seconds per movement could
represent 4-5 additional operations during a busy time-period, which is the most valued by
passengers and airlines.
Clearly, only a good organisation of the arrival flow can maximise runway throughput whilst
keeping delays at a minimum. The management of arrival flows into airports is driven by a
multitude of factors and developing the best strategy appears to be a network as well as a
local issue.
There are several important issues, which will be addressed in the following sections:
• Delivering traffic from the network to airports as close to the scheduled times as
possible;
• Techniques to maintain a continuous stock of arrival traffic close to the airport;
• Seamless movement from the holding areas to the final approach;
• Optimisation of the traffic mix, i.e. wide bodies should be grouped in order to
minimise the time interval between landing aircraft;
• Separation on final approach should be as close as possible (but not less than) the
minimum separation that can be applied in the given circumstances; and,
• Use of ATFM airport regulations to protect the airport’s available capacity.
2.4.1. En route sequencing
At present, there is almost no en-route sequencing in Europe. Where it exists, it results
from specific agreements between neighbouring ACCs. En-route speed control with
required time of arrival (RTA) could for example reduce variations in arrival times on
transatlantic flights27, provided RTA is applied well in advance.
En-route sequencing is common practice in the US where it is called either Miles in Trail
(MIT) or Times in Trail. Miles in Trail describes the number of miles required between two
consecutive aircraft on a given traffic flow, which is in most cases defined on the basis of
flights with the same arrival destination. MIT is used to organise a steady flow, as well as to
provide space for additional traffic (merging or departing).
MIT can also affect aircraft on the ground when an En-route Spacing Program (ESP) is
activated. If an aircraft is about to take-off from an airport to join a traffic flow on which a
MIT restriction is active, the aircraft needs specific clearance for take-off. The aircraft is
only released by ATC when it is possible to enter into the sequenced flow. The impact of
MIT on quality of service could be either airborne or taxi-out delays. The benefits for the
airport arrival flow are high. Firstly, there is very limited interruption in the upstream flow so
that a continuous arrival flow is ensured. Secondly, MIT is designed in a way that traffic is
streamed well before arriving at the last approach ATC unit.
27
Eastbound transatlantic traffic is not affected by ATFM regulations as the departure airports are not in the
EUROCONTROL area. Some flights from dep airports outside the CFMU area may be subject to ATFM
slot allocation.
- 15 -
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
2.4.2. Circular airborne holdings to stock arrival demand
In Europe, some airports use circular airborne holdings to stock traffic in order to supply the
airport with continuous demand.
In general, the amount of aircraft that can be stocked depends on the number of holdings
and the ability of en-route ATC sectors to ensure a continuous traffic flow bound for circular
holdings.
Due to such airspace and ATC organisation, UK NATS are able to maintain at least 10-15
aircraft in holdings close to London Heathrow airport. Figure 2-9 shows the circular
holdings at London Heathrow airport,
Although circular holdings are available at all IFR airports in Europe, many airports use
these holdings only where there is a sudden unavailability of runway capacity (e.g.
unexpected deteriorations of weather or unpredicted excess of demand or in case of
change of runway configuration).
Circular holdings are always associated to given entry points in the terminal airspace. If a
holding becomes too busy, it then becomes necessary to move traffic in less crowded
holdings. This can easily be done if the airspace design is appropriate and when all entry
points are managed by the same ACC.
Figure 2-9: Circular holdings at London Heathrow airport
Stack switching requiring real-time co-ordination between ACCs is not applied in Europe.
Therefore, when there is a foreseeable risk that a given holding pattern becomes
overloaded, ATFM regulations are usually imposed.
2.4.3. Combined use of circular and linear holdings to stock and sequence arrival demand
Linear stacks combined with circular holdings are useful to stack and to sequence the
arrival traffic at the same time. This avoids potential wastage of capacity when directing the
demand from the circular holdings to the final approach. An efficient use of linear stacks
requires the use of approach sequencing tools.
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AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
Figure 2-10 shows the combined use of linear and circular holdings at Frankfurt airport28.
Figure 2-10: Linear and circular holdings at Frankfurt airport
Airports that are not equipped with linear stacks and/or approach sequencing tools rely on
the expertise of approach and TMA ATCOs to organise the arrival sequence.
Both linear and circular holdings ensure minimal waste of capacity, because they can be
implemented at relatively short notice to deal with excess demand. Circular and linear
holdings impact on the service quality. If the expected amount of traffic or the anticipated
level of airborne delay is too high for available facilities, or safety is at stake, an ATFM
regulation is usually issued. This could be due to the en-route sectors delivering too much
traffic compared to scheduled demand.
2.4.4. Separations on final approach and traffic bunching
Thus far, the efficient delivery of traffic to the final approach has been discussed. However,
the volume of traffic to be delivered to the final approach should be close to the minimum
standard separations but not lower.
In the case of mixed traffic, the maximum throughout on final approach can be achieved by
grouping wide-bodies, and by landing light aircraft on remote runways. The study did not
look at these aspects in any detail.
2.4.5. Use of ATFM airport regulations to protect the airport short term capacity
The CFMU is generally not aware of the extent to which local flow/ATC measures are in
use at the individual airports. The interaction between the local flow unit and the CFMU
only takes place when there is a need to introduce an ATFM airport regulation.
ATFM airport regulations should only be used when it is anticipated that there will be a
significant mismatch between available arrival capacity and demand, which cannot be
handled by local flow/ATC measures. To be effective, they have to be applied at least two
hours in advance.
28
In case of a foreseeable overflow of holding patterns ATFM regulations might be applied.
- 17 -
AIR TRAFFIC SCHEDULING AND ATM PROCESSES
Punctuality drivers at major European airports
When an ATFM airport arrival regulation is in place, aircraft are held at the departure
airports, which reduces traffic demand significantly at the airport that has issued the
regulation.
ATFM airport regulations are not designed to ensure a continuous traffic demand to the
arrival airport which is necessary to maximise airport operations.
- 18 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
3. MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
This chapter presents the concept of “air transport punctuality” as currently used to
measure performance. It discusses the suitability of “punctuality” to measure air transport
performance. It then introduces a high-level framework for the analysis of operational air
transport performance. The chapter also contains analysis of departure and arrival
punctuality at 11 major European airports, to set the scene for more detailed analysis.
3.1.
Air transport punctuality
The generally accepted performance indicator for the operational performance of airlines
and airports is “punctuality”. Air transport punctuality is usually defined as the proportion of
flights delayed by more than 15 minutes compared to airline scheduled departure and
arrival times.
Since air transport punctuality is measured with respect to the airline schedule, two key
values are usually measured:
•
•
Departure punctuality: the difference between the actual off block time and the
scheduled off block time; and,
Arrival punctuality: the difference between the actual on-block time and the
scheduled on block time.
In 2004, on average 23% of outbound flights (departure punctuality) and 20% of inbound
flights (arrival punctuality) had a delay higher than 15 minutes compared to the schedule29.
% of flights with arrival delay > 15 min
Overall, punctuality is affected by a large number of different drivers, as illustrated in Figure
3-1 below. After a continuous improvement of overall punctuality between 2000 and 2003,
punctuality decreased in 2004.
30%
AEA
eCODA
25%
20%
15%
10%
5%
0%
2000
2001
2002
2003
2004
Reactionary
Other Causes
Local drivers at destination airport
En-route delay
Local drivers at departure airport (airlines, airport, security, etc.)
data source: AEA (->2001), eCODA
Figure 3-1: Evolution of air transport punctuality and underlying drivers
Reactionary delay30 and local drivers at departure airports (airline, airport, security, etc.)
appear to be the key drivers of punctuality. The contribution of en-route delays (ATFM)
could be reduced steadily between 2000 and 2004.
It can also be noted that the contribution of local drivers at arrival airports increased rapidly
between 2000 and 2004 to become higher than en-route delays in 2004.
29
30
Source: eCoda 2004 which covers approximately 50-60% of commercial air traffic in Europe.
Reactionary delays are caused by the late arrival of aircraft or crew from previous journeys.
- 19 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
In almost all aviation publications, a flight is “on-time” when it is less than 15 minutes
behind schedule. This report considers another dimension, namely flights arriving more
than 15 minutes ahead of schedule. This can, depending on the airports concerned, be
also a problem for air transport operations.
In order to explore this dimension further, the following section analyses the data in three
separate groupings:
• Flights more than 15 minutes ahead of schedule;
• Flights on time (-15 / +15 minutes); and,
• Flights more than 15 minutes behind schedule.
3.2.
Punctuality as a measure of service quality in air transport
From a passenger viewpoint, safety, price and adherence to the published schedule
(punctuality) are among the most important selection criteria when choosing an airline.
There are many factors contributing to the punctuality of a flight, on which aircraft operators
or airports have limited or no influence. In reality, air transport punctuality is the “end
product” of a complex interrelated system, involving many different stakeholders of the
aviation community.
Due to the high degree of public interest, it is in an airline’s best competitive interest to
operate flights within the commonly accepted 15-minute punctuality window of its published
schedule times. To achieve an acceptable level of punctuality, airlines often include
“strategic” time buffers in their schedules in order to account for a predictable level of delay.
Consequently, if a flight frequently experiences delays, which has an adverse impact on the
punctuality record, the airline will adjust the scheduled time for the flight to reflect this. The
addition of a larger schedule “buffer” allows the airline to maintain a good on-time
performance (punctuality record), even though some flights routinely encounter congestion
and delays. Hence, the “scheduled” time for a flight (block-to block) is not the same as the
actual amount of time that is required to make the trip in normal conditions and without any
delays or congestion.
There are many factors contributing to a flight’s punctuality and it is important to
understand the difference between airline schedules, which form the basis for the
measurement of punctuality, and actual travel times.
From an analytical point of view, the adjustment of schedules to compensate for expected
congestion and/or flight operation variability makes air transport punctuality only of limited
use for the measurement of operational air transport performance. Punctuality targets or
equivalent quality of service parameters are airline business decisions, varying among
airlines. The “masking” of the true amount of flight operation variability by including
strategic time buffers into schedules makes it difficult to measure accurately the effect of
new processes and strategies intended to improve system performance.
OUT
Schedule
ON
OFF
Taxi Out
Airborne
IN
Taxi In
ON Time
Buffer
Early arrival
Late arrival
Ahead of
schedule
Delay
Behind
schedule
Figure 3-2: Punctuality and air transport operations
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MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
Punctuality is a valid indicator from a passenger viewpoint. However, punctuality alone is
not an appropriate indicator to measure and to improve operational air transport
performance. It is better to focus on the variability of operations.
It is normal that flights in daily operations are subject to a certain level of variability, due to
the stochastic nature of air transport (weather, technical failures, etc.) and the multiplicity of
stakeholders involved (operational procedures, sequencing criteria, etc.) [for further reading
see Ref. x]. Consequently, a specific flight leg is not entirely predictable.
Furthermore, the late arrival of an aircraft often causes delays in the next departure of this
aircraft, and sometimes delays for connecting flights. Such delays are referred to as
reactionary delays.
Variability, and hence the predictability of flight operations, is of major importance in airline
and airport scheduling. Tightening the distribution of arrival times around an optimum value
allows time buffers in block times to be reduced while maintaining punctuality.
The stakes are high. The cost of one minute of buffer time for an A320 is estimated at €49
per flight. Cutting five minutes on average off 50% of schedules thanks to higher
predictability would be worth some €1 000M per annum, through savings or better use of
airline and airport resources.
3.3.
High level framework for the analysis of air transport operational performance
Although the reduction of variability of flight operations does not necessarily improve
punctuality (as block times are adjusted by airlines according to their punctuality target),
considerable savings could be realised because of the reduced need for strategic buffers in
flight schedules.
To analyse the different drivers of variability of flight operations, a conceptual framework is
introduced. Although the framework is high level and does not capture every individual
source of variability separately, it takes a system perspective and gives a better
understanding of the variability of the individual flight phases and their importance for the
daily operations (see Figure 3-3).
Scheduled turn
around times
Other
airline, airport
reactionary, etc.
Variations in TAXI -IN
times
ATFM delay
En-route/Airport
Drivers of block-time variability
(after push-back)
Variations in terminal
transit times
Turn
around
times
Departure
punctuality
Variations in
en-route times
Pre-departure
delays
incl. strategic time buffers
Variations in TAXI -OUT
and holding times
Drivers of departure
variability (before push-back)
Scheduled block times
Arrival
punctuality
Turn
around
times
Figure 3-3: High-level conceptual framework for the analysis of air transport performance
In a first step, a distinction is made between drivers of variability before push-back (“predeparture delays”) and variability of flight phases after push-back (after the aircraft has left
the gate).
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MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
Using IATA delay categories as a basis, “pre-departure delay” is further broken down in this
report according to its origin:
•
•
•
Pre-departure delay (airport, airline, local ATC, other primary delay, reactionary31);
Delays due to en-route ATFM regulations; and,
Delays due to ATFM regulations at the destination airport.
The study does not intend to go into a more detailed level of analysis at this stage. More
sophisticated analysis based on more comprehensive data beyond the IATA delay coding
would be required. Many airports and airlines already scrutinise their internal processes in
order to improve their performance. European Collaborative Decision making (CDM)
projects should be mentioned here, as they strive to improve the way airlines, airports and
ATM work together at operational level at airports.
The variability of flight phases after the flight goes “off-block” is further broken down
according to the operational environment:
1. Variability in the “time to take-off”32 at the departure airport. This variability is
affected by the departure terminal, runway configuration33, taxiway congestion, deicing, runway separations, wake vortex mix, etc.
2. Variability in the cruising phase. The cruising phase is mainly affected by route
availability, route selection (e.g. longer route with cheaper route charges or less
ATFM delay) and strong winds (long haul).
3. Variability in the terminal airspace. This phase is affected by the trade off between
maximising runway capacity and airborne delay (which has been set during the
scheduling phase), actual arrival flow and the management of bad weather
conditions.
4. Variability in the “taxi-in”34 phase. The taxi-in phase is mainly related to the runway
configuration in use, taxiway congestion and gate availability.
While it would be desirable to analyse the cruising phase and the terminal airspace
separately, it was not possible in this study to make this distinction due to the lack of
necessary data. Both cruising phase and terminal airspace are included in “flight times”
variability. Previous analysis however suggests that, with the exception of long-haul traffic,
variations in the terminal airspace are more significant than variations in the cruising phase.
Data on transit times in major terminal areas will be required for more detailed analysis with
a view to performance improvement.
The next section presents an initial evaluation of time variability in flight phases (departure,
taxi out, airborne and arrival), in order to identify the main influencing flight phases.
31
32
33
34
Reactionary delays are a special case. They are the result of primary delays most likely experienced at
different airports.
From off-block to take-off.
When the wind is blowing from the East, a flight from Paris to Brest needs at least 6 minutes more in the
terminal areas than when wind is blowing from the West.
From landing to on-block.
- 22 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
3.4.
Origin of variability of flight phases
The standard deviation relates to the “width” of the distribution of the sample, and
constitutes a first level indicator of variability within the sample35.
30
Standard deviation in minutes (2004)
Intra European Flights
Transatlantic Flights
25
20
15
10
5
0
Departure time
Taxi out + holding
Flight times (enroute + terminal)
Taxi in + waiting for
gate
Arrival time
Figure 3-4: Variability of flight phases (eCoda)
As shown in Figure 3-4, the taxi-in and taxi-out phases of Intra-European flights introduce a
non-negligible level of variability, but are relatively low compared to other flight phases.
However, this varies by airport and depends clearly on local circumstances36. Variability for
transatlantic flights is observed to be significantly different in all phases of flight.
Figure 3-4 shows that the variability of arrival times is mainly influenced by:
•
•
Departure time variations driven by pre-departure delays (i.e. airline/airport related
delay such as technical failures, ATFM delay, reactionary delay, etc.); and,
Variations in the flight times (cruising plus terminal airspace). In particular, long haul
flights such as transatlantic flights bound for Europe show a much higher variability
than Intra-European flights, which is due to strong winds during the flight phase.
Figure 3-5 shows that the departure time variability (and therefore the arrival time
variability) can change considerably throughout the year. For example, although bad
weather is not entirely predictable, the fact that it is on average worse in the winter months
seems to be one of the reasons for the observed variations.
35
36
In a normally distributed sample.
The analysis for this study has identified that taxi-out and taxi-in phases are an issue at some airports only.
- 23 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
Average monthly variability of flight phases (2002 -2004)
30
20
15
10
5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Standard deviation (minutes)
25
2002
2003
2004
Departure times
Taxi in
Taxi out & holding
Arrival times
Flight phase (en-route & terminal)
Figure 3-5: Variability of flight phases by month (eCoda)
In summary, the main drivers of variability of flight operations appear to be:
• departure time variability driven by pre-departure delays (local airline/airport related
issues, ATFM delay, and reactionary delay).
• variations in flight times which includes the cruising phase (in particular for long-haul
flights) and variations in terminal airspace transfer times.
Once the sources of variability have been identified, it is necessary to determine if and to
what extent they can be reduced and/or foreseen. Variability of flight operations may be the
result of causes which cannot be controlled or of causes that could be removed or at least
reduced by implementing new processes and policies.
The study focuses on ATM related issues. For the sake of completeness, issues such as
airport or airline drivers will also be briefly touched upon.
Punctuality at major European airports
The following section provides an overview of operations and aircraft mix at the 11
analysed airports (see Table 3-1). It then looks at departure and arrival punctuality.
Active
Runways
Airport
Total IFR mvts.
(2004)
Peak daily mvts.
(2004)
Heavy
Medium
Light
Amsterdam - AMS
5
412,810
1,303
18.3%
80.8%
0.9%
Barcelona - BCN
2
293,025
963
1.6%
96.2%
2.2%
Paris/Charles-De-Gaulle - CDG
4
526,471
1,666
20.4%
79.5%
0.1%
Rome/Fiumicino - FCO
4
310,086
990
7.9%
92.1%
0.0%
Frankfurt - FRA
3
488,823
1,475
27.3%
72.2%
0.5%
London/Heathrow - LHR
2
476,100
1,378
32.8%
67.1%
0.1%
Madrid/Barajas - MAD
3
403,171
1,305
10.0%
89.8%
0.2%
Munich - MUC
2
379,625
1,267
6.6%
91.9%
1.5%
Milan/Malpensa - MXP
2
218,399
750
13.2%
86.0%
0.7%
Vienna - VIE
2
241,151
845
4.8%
92.0%
3.2%
3
254,995
815
8.8%
87.0%
4.2%
Zurich - ZRH
Table 3-1: IFR movements and aircraft mix
- 24 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
Airport infrastructure and traffic mix affect punctuality at airports. A comparatively higher
share of heavy traffic (wake vortex category) is observed at London Heathrow and
Frankfurt, which corresponds to higher intercontinental traffic. Intercontinental traffic causes
variations in airport capacity (higher wake vortex separations) and generates higher
variability.
While almost no flights depart early (Figure 3-6 right side), a considerable number of flights
arrive more than 15 minutes ahead of schedule (yellow bars, Figure 3-6 left side). Early
arrivals appear to be an issue at some airports. Early arrivals can put additional pressure
on airport, airline, ATC and handler resources: the local ATC has to cope with an
unexpected demand profile, gates are occupied longer than planned, and additional
resources are needed to cope with unforeseen workload (e.g. baggage handling). More
importantly, a combination of late arrivals in the preceding period and of early arrivals in the
following period can lead to excess demand in a particular period, as illustrated in Figure
4-3.
Dep. Punctuality (all outbound flights)
8%
16%
7%
8%
6%
12%
90%
10%
8%
8%
8%
9%
Arrival Punctuality (all inbound flights)
100%
82%
74%
80%
80%
74%
76%
77%
81%
73%
76%
72%
76%
67%
70%
75%
73%
74%
50%
70%
71%
70%
70%
60%
63%
70%
40%
18%
26%
20%
25%
CDG
MXP
24%
FCO
20%
23%
MAD
BCN
19%
FRA
26%
24%
16%
MUC
VIE
17%
AMS
28%
18%
MXP
LHR
18%
21%
FCO
BCN
21%
MAD
18%
21%
FRA
CDG
22%
ZRH
10%
22%
20%
VIE
30%
28%
% of flights (2004)
80%
MUC
AMS
ZRH
LHR
0%
Flights more than 15 min. ahead of schedule
Flights within -/+15 min. of schedule
Flights more than 15 min. behind schedule
Data source: EUROCONTROL/ eCODA
Figure 3-6: Arrival and departure punctuality
Figure 3-6 raises some interesting questions:
1. What is a good level of punctuality?
2. What resources and processes are needed to maintain a good level of punctuality?
3. If the variability of operations is reduced, will the punctuality improve or will the
block times get adjusted while maintaining a similar level of punctuality?
- 25 -
MEASURING AIR TRANSPORT OPERATIONAL PERFORMANCE
Punctuality drivers at major European airports
Figure 3-7 shows the links between departure delays (at origin airport) and arrival delays of
flights inbound to the 11 analysed airports. Departure delay causes are identified, but
arrival delay causes could not be.
Departure punctuality of
outbound
flights at analysed airports
Arrival punctuality of inbound
flights at arrival airports
30%
FLIGHT PERSPECTIVE
25%
21.7%
21.0%
20.6%
20.6%
18.5%
18.1%
18.0%
17.1%
16.0%
Dep. to
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
Dep. to0.0%
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
Dep. to
Arr. at
Dep. from
10%
Dep. to
Arr. at
Dep. from
22.4%
15%
27.8%
20%
ZRH
FRA
MAD
FCO
CDG
BCN
MXP
AMS
5%
Dep. to
Arr. at
Dep. from
0%
Dep. to
Arr. at
Dep. from
% of flights departing/ arriving more than
15 min. behing schedule (2004)
Departure punctuality of inbound
flights at departure airports
LHR
VIE
Drivers of
departure delay:
MUC
Reactionary delay
Other Causes
Local drivers at destination airport (ATFM regulations due to weather or capacity)
En-route delay (ATFM regulations due to weather or capacity)
Local drivers at departure airport (airlines, airport, security, etc.)
Figure 3-7: Mutual influence of departure and arrival punctuality
The figure above shows the rotations of flights at the 11 airports. The left bars represent
pre-departure delays for incoming traffic, the blue bars represent the punctuality of arrival
traffic while the right bars represent the pre-departure delays for outgoing traffic.
In general, the largest share of departure delay originates from airline and airport
operations at departure (yellow bars), and from reactionary delays from earlier flights (grey
bars)
The green bars show the proportion of departure delay related to the arrival airport (ATFM
regulations due to weather or capacity).. As pointed out before, arrival punctuality (blue
bars) is primarily driven by departure punctuality of incoming traffic and further affected
(positively or negatively) by time variations after leaving the gate.
One late arrival may cause more than one late departure for connecting flights at hub
airports. At some airports, especially at Amsterdam and Paris CDG, outbound departure
delays are higher than arrival delays. At some airports, especially Amsterdam and Zurich,
the proportion of reactionary delays is higher for outgoing traffic than for arrivals. This
amplifies delays in the network during the day.
- 26 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
4. DRIVERS OF VARIABILITY BEFORE PUSH-BACK (PRE-DEPARTURE DELAYS)
The following sections analyse the sources of departure time variations (before the flight
goes off-block) in accordance with the analytic framework in Section 3.3:
• ATFM regulations and delays;
• Airline, airport and other causes; and,
• Reactionary delay.
4.1.
ATFM regulations and delays
ATFM regulations and hence ATFM-related delays essentially occur when traffic demand
exceeds ATM capacity en-route (en-route ATFM delay) or at departure/arrival airports
(airport ATFM delay), if no alternative measures are available. This may be due to overdeliveries from the network or a structural lack of capacity, technical failures, industrial
action, staff shortages or adverse weather.
ATFM measures applied to en-route sectors include re-routing, level capping and ATFM
regulations. It is important to understand that aircraft subject to ATFM regulations are
always held at the departure airport according to “ATFM slots” allocated by the CFMU. The
ATFM delay of a given flight is allocated to the most constraining ATC unit, either en-route
(en-route ATFM delay) or departure/arrival airport (airport ATFM delay).
As pointed out previously, ATFM delays are pre-departure delays and do not necessarily
correspond to the total delay as perceived by the passengers.
It is possible to measure accurately ATFM delays, because they are centrally managed by
the CFMU (see Section 1.2.). The level of ATFM delay can be used as an indicator to
identify areas where improvements should be made to the ATM system. ATFM delays can
have a significant “knock-on” effect and hence cause extensive reactionary delays to the
network (see Section 4.3). It is important to clarify that ATFM delays do not correspond to
the total delay attributable to ATC operations.
4.1.1. Inbound traffic affected by en-route and airport ATFM delays
Figure 4-1 shows the impact of ATFM regulations on arrival punctuality, which is
particularly high at London Heathrow, Zurich and Vienna.
The en-route ACC(s) causing the delay could be anywhere along the planned flight path,
but also in the vicinity of the airport itself. Where high levels of en-route delays are
observed, it might be interesting for the airport to trace the exact source of the problem in
order to see whether it can be resolved or mitigated.
- 27 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
30%
Flights with an arrival delay
>15 min. (2004)
25%
20%
15%
10%
5%
0%
LHR
VIE
ZRH
FRA MAD FCO CDG BCN MXP AMS MUC
Other delays (airline, airport, reactionary, technical etc.)
En-route ATFM regulation
Airport ATFM regulation (due to weather)
Airport ATFM regulation (due to ATC/Aerodrome capacity)
Data source: EUROCONTROL/ eCODA
Figure 4-1: ATFM delays affecting inbound traffic into the analysed airports
At some airports, more than 5% of arrival flights are delayed because of a lack of actual
capacity at the arrival airport (airport ATFM regulations due to weather or local
ATC/aerodrome capacity). The high level of weather-related arrival delays at some airports
deserves to be further investigated.
4.1.2. Airport ATFM delays caused by the analysed airports
Almost all airport ATFM delays are caused by regulations at the arrival airport. This is why
this report concentrates on arrival airport ATFM delays. Paris Charles de Gaulle is the only
airport showing a significant level of ATFM airport departure delay. This phenomenon
should be further investigated.
Figure 4-2 shows a year on year comparison of ATFM airport arrival delays at the 11
airports analysed in this report. In 2004, those 11 airports accounted for 25% of aircraft
arrivals in Europe; however, they generated 75% of all arrival airport ATFM delays.
- 28 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
4 min.
1 100
2003
2004
3 min.
900
Frankfurt
800
700
Zurich
600
2 min.
London/Heathrow
Vienna
500
Madrid/Barajas
400
Rome/Fiumicino
300
Paris/Charles-De-Gaulle
Munich
Milan/Malpensa
1 min.
Amsterdam
Average arrival ATFM airport delay
Arrival ATFM airport delay ('000 minutes)
1 000
Barcelona
200
100
0
0
50
100
150
200
Arrival Traffic ('000 flights)
250
300
Data source: EUROCONTROL
Figure 4-2: Evolution of traffic and arrival airport ATFM delays (2003-04)
This figure highlights the high level of delays originating from some airports, eg more than 3
minutes per flight at Frankfurt while the average airport ATFM arrival delay was 0.8 minutes
in 2004.
Despite a significant reduction in airport ATFM arrival delays, Frankfurt still generated the
highest level of airport ATFM arrival delay in 2004, followed by London Heathrow, Zurich
and Vienna.
Airport ATFM arrival delays increased significantly at Vienna, Zurich, Madrid37 and London
Heathrow airport. The delay increase at Vienna is related to a significant increase in traffic
(+13%), not matched by a corresponding increase in terminal area capacity. Zurich had 1%
less traffic and 59% more ATFM delays, mostly due to heavy environmental restrictions.
The most significant improvements are observed at Paris CDG (increased staff in
approach), Rome Fiumicino (resolved inconsistency between the ATC capacity and the
airport capacity), Milan Malpensa and Frankfurt.
4.1.2.1.
Decision making process when managing arrival flows at airports
A capacity/demand imbalance normally originates from temporary excess demand or
reduced capacity, as shown in Figure 4-3. There may also be cases of overscheduling.
37
The analysis of ATFM airport arrival delay at Madrid airport includes regulations allocated to an en-route
reference location in the vicinity of the airport to protect the airport’s arrival capacity.
- 29 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
“Excess demand”
Use of tools to
reestablish balance
Early
flights
Delayed
flights
Anticipated
demand too high
(Over-deliveries)
06 07 08
Available capacity
(normal conditions)
“Reduced capacity in adverse weather”
Declared capacity
Anticipated
reduction of
available capacity
(bad weather etc.)
Bad weather capacity
Use of tools to
reestablish balance
Figure 4-3: Imbalance between demand and capacity
When a capacity shortfall at an airport is forecast, some critical decisions have to be taken
by the ATC supervisor/flow manager in charge in order to maintain safety. Essentially, a
balance has to be struck between holding aircraft on the ground or in the air, as shown in
Figure 4-4. The decision has to be taken at least two hours in advance for an ATFM
regulation to be effective. These decisions have considerable influence on the airport’s
acceptance/arrival rate and thus on the efficiency of operations.
Quality of
forecast
ATFM regulation most
appropriate tool and parameters
correct (magnitude/ duration)
Traffic
forecast
ATFM
regulation
Anticipated
imbalance
btw. demand &
capacity
ATFM regulation most
appropriate tool but parameters
incorrect (magnitude/ duration)
ATFM regulation issued but more
appropriate tool available
Flow manager/
ATC supervisor
Availabililty of circular holdings
Airport
declared
capacity
Available
capacity
Quality of
forecast
MET
forecast
Terminal
airspace
Availability of linear stacks
Availability of safeguard options such as the
possibility to operate a “ground stop” from
departing airports.
Figure 4-4: Selecting the most appropriate tools to balance capacity and demand
Where there is an anticipated capacity imbalance due to over deliveries, the CFMU
demand forecast and expertise based on previous experience is often the only input
available to decision takers. Hence, the accuracy of the forecast two or more hours before
the actual event is crucial for the flow manager’s decision-making. It is important to strive to
optimise the accuracy of the CFMU demand forecast, by including for example more
accurate taxi out times38 and as much real time data as possible. The Enhanced Tactical
Flow Management System (ETFMS) currently being implemented by the CFMU correlates
38
The CFMU’s current traffic forecast is based on standard taxi out times for each airport which might vary
significantly from the actual taxi out times, depending on the runway configuration in use.
- 30 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
live radar data from all over Europe. However, it has serious limitations in monitoring arrival
traffic close to airports, which the CFMU is working to overcome. A possible future
improvement could also be the integration of anticipated turn-around times, which would
allow a truly system-wide demand forecast.
Where there is an anticipated capacity reduction due to weather, the flow manager usually
has to base his decision on meteorological forecasts. It is often difficult to predict the
duration of weather phenomena with the requisite accuracy. However, experience at some
airports, e.g. Amsterdam, shows that proactive integration of state-of-the-art MET
information in the decision process has the potential to considerably reduce unnecessary
capacity wastage due to inaccurate ATFM regulations.
The quality of decision making in calling for ATFM regulations, and the balance of ground
and airborne delays have to be systematically assessed through post-event analysis.
4.1.2.2.
Causes of ATFM regulations
When an ATFM regulation is issued, the CFMU assigns a delay code in order to identify
the reason for the regulation. For the purposes of this analysis, those codes were used to
calculate the delay assigned to one of three delay groups:
• ATC/Aerodrome capacity related airport arrival ATFM delays39;
• Weather-related airport arrival ATFM delays; and,
• ‘Other’ airport arrival ATFM delays.
Minutes of ATFM airport arrival delay ('000)
Furthermore, in each regulation request from a local Flow Management Position (FMP),
there is an optional field to describe the reason for the delay. This is a non-standardised
field and is left to the discretion of the FMP. The descriptions in this field allow a further
breakdown of weather-related regulations into strong wind, low visibility or other/multiple
weather related delays. Figure 4-5 shows the amount of ATFM airport arrival delay
generated by each of the analysed airports for the previous three years.
1 100
1 000
900
800
700
600
500
400
300
200
100
2002
2003
2004
2002
2003
2004
FCO
MAD
MXP
MUC
AMS
CDG/LBG*
ATC/Aerodrome capacity
Weather - Wind
Weather - Other or Multiple
Others
2002
2003
2004
2002
2003
2004
VIE
2002
2003
2004
ZRH
2002
2003
2004
2002
2003
2004
LHR
2002
2003
2004
2002
2003
2004
FRA
2002
2003
2004
2002
2003
2004
0
BCN
Weather - Vis/Fog
* includes joint regulations with Paris Le Bourget - Data source: CFMU
Figure 4-5: Arrival airport ATFM delays by cause of delay (2002-04)40
39
40
It was decided to combine ATC and Aerodrome causes as there were no clear cut definitions for the exact
assignment at some airports.
The analysis of ATFM airport arrival delay at Madrid airport includes regulations allocated to an en-route
reference location in the vicinity of the airport to protect the airport’s arrival capacity.
- 31 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
The reasons why airports issue arrival ATFM regulations vary significantly among the
analysed airports. Whereas in Amsterdam almost all of the airport ATFM arrival delay is
due to weather-related ATFM regulations, most of the delay at Milan Malpensa is the result
of ATC/ Aerodrome capacity limitations.
‘Other’ ATFM airport arrival delay represents the smallest share of ATFM airport arrival
delays. It refers generally to special or unforeseen events, such as ATC equipment failure
or an increase in air traffic due to a major sporting event.
4.1.2.3.
Excessive use of ATFM regulations
Figure 4-6 shows a breakdown of ATFM regulations applied during 2003 and 2004 at the
eleven airports in question. With the exception of Munich, Amsterdam, London Heathrow
and Frankfurt, most airports apply ATFM regulations due ATC/aerodrome restrictions
nearly every day.
350
Nr. of days with ATFM airport
arrival regulations
300
250
200
150
100
50
MUC
AMS
LHR
FRA
BCN
ATC/Aerodrome related regulation
Weather and other
No ATFM regulation
MAD
FCO
CDG*
MXP
VIE
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
2003
2004
0
ZRH
Weather only
Other and Multiple causes
* includes joint regulations with Le Bourget Airport - Data source: CFMU
Figure 4-6: Breakdown of arrival ATFM regulated days in 2003 and 200441
It is noteworthy that many co-ordinated airports in Europe regularly apply ATFM arrival
regulations due to ATC/aerodrome capacity restrictions. These restrictions should normally
be dealt with during the airport capacity declaration process. It seems that there is scope
for improvement in this area. Excessive use of ATC/Aerodrome related airport arrival ATFM
regulations might be due to:
•
•
•
•
•
41
A misunderstanding of the effectiveness of ATFM regulations. They can neither
create a continuous demand nor finally control flows when demand slightly exceeds
capacity (see Ref. ii);
A lack of knowledge of the high impact of pre-departure delay on the level of
punctuality;
A lack of arrival tools and procedures to handle and prepare a steady arrival flow;
A lack of interaction in the strategic phase between the ANSP, airports and airlines.
During the airport capacity declaration process, it might not be clear to the airport
community how demand exceeding the runway capacity will be handled by the local
ATC:
Over-statement of scheduling capacity.
The analysis of ATFM airport arrival delay at Madrid airport includes regulations allocated to an en-route
reference location in the vicinity of the airport to protect the airport’s arrival capacity.
- 32 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
Figure 4-7 shows the distribution of airport ATFM arrival delayed flights in 2004 by delay
duration and delay cause for the analysed airports. Overall, weather-related airport ATFM
arrival regulations (right side) tend to be longer than ATC/Aerodrome-related regulations
(left side).
At Barcelona, Paris Charles de Gaulle, Amsterdam and Milan Malpensa, the proportion of
flights with short airport ATFM delays (less than 10 minutes) is particularly high42. Short
ATFM delays are unable to reduce a slight excess of demand and generate a significant
level of delay (see Section 4.7 of PRR 7 [Ref. ii]).
20%
10%
10%
0%
0%
FRA
01-10 (min.)
31-60 (min.)
ZRH
30%
20%
FCO
40%
30%
MXP
40%
CDG
50%
BCN
50%
AMS
60%
ZRH
60%
FCO
70%
MXP
70%
CDG
80%
BCN
80%
AMS
90%
LHR
100%
LHR
Weather-related ATFM regulations
90%
FRA
% of flights with airport ATFM arrival delay
ATC/Aerodrome related ATFM regulations
100%
11-30 (min.)
>60 (min.)
Figure 4-7: Distribution of airport ATFM arrival delay durations in 2004
In 2004, a substantial proportion of flights was delayed by more than 60 minutes, mostly
due to weather related ATFM airport arrival regulations. This proportion is relatively higher
in Rome Fiumicino, Amsterdam, Milan Malpensa and Paris Charles de Gaulle, as shown in
Figure 4-7. These long ATFM delays generally cause strong knock-on effects to airline and
airport operations, and to the European network (reactionary delays).
In order to keep weather-related delays to a minimum whilst maintaining safety at all times,
the drop of capacity during bad weather should be minimised and ATFM regulations
applied as accurately as possible (see also chapter 2.1.2).
The use of ATC/Aerodrome capacity related airport ATFM arrival regulations due to an
anticipated over-delivery in normal conditions is a different matter. They should not occur
frequently at a coordinated airport, and then only in exceptional circumstances (i.e. closure
of a runway, technical failures).
The following section uses Frankfurt and Milan Malpensa as examples. Figure 4-8 shows
the distribution of ATC/Aerodrome related ATFM airport arrival regulations at Frankfurt
during 2003 and 2004. Frankfurt is interesting because there was a change in policy
leading to a more cautious use of ATC/Aerodrome related ATFM regulations in 2004.
Detailed analysis of demand patterns combined with co-ordinated action such as the depeaking of scheduled arrival demand at Frankfurt confirmed that a considerable number of
those regulations were avoidable.
42
However, it should be pointed out that Amsterdam has a comparatively small amount of ATC/Aerodrome
related ATFM arrival delay compared to the other airports (see also Figure 4-5).
- 33 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
The number of regulations issued at Frankfurt due to ATC/Aerodrome related reasons
could be reduced significantly in the second half of 2004, yielding positive results in terms
of ATFM delays. However as pointed out previously, it is important to monitor terminal
holding delays as there has to be a balance between ground and airborne delays.
FRA - ATFM arrival regulations due to ATC/Aerodrome capacity (2003/04)
24:00
1440
23:00
1380
2003
1320
22:00
2004
21:00
1260
1200
20:00
1140
19:00
1080
18:00
1020
17:00
960
16:00
900
15:00
840
14:00
780
13:00
720
12:00
660
11:00
600
10:00
540
09:00
480
08:00
01-12-04
01-11-04
01-10-04
01-09-04
01-08-04
01-07-04
01-06-04
01-05-04
01-04-04
01-03-04
01-02-04
01-01-04
01-12-03
01-11-03
01-10-03
01-09-03
01-08-03
01-07-03
01-06-03
01-05-03
01-04-03
01-03-03
01-02-03
360
06:00
300
05:00
01-01-03
420
07:00
Figure 4-8: ATC/Aerodrome capacity related airport regulations at Frankfurt
Figure 4-9 shows the profile of ATC/Aerodrome capacity related airport ATFM arrival
regulations for Milan Malpensa during 2003 and 2004. Here, the systematic use of
relatively short regulations of which a high number are cancelled before the end (see next
section) at almost the same time of the day suggests scope for improvement.
MXP - ATFM arrival regulations due to ATC/Aerodrome capacity (2003/04)
24:00
1440
23:00
1380
2003
1320
22:00
2004
21:00
1260
1200
20:00
1140
19:00
1080
18:00
17:00
1020
960
16:00
900
15:00
840
14:00
780
13:00
720
12:00
660
11:00
600
10:00
540
09:00
480
08:00
420
07:00
Figure 4-9: ATC/Aerodrome capacity related airport regulations at Milan Malpensa
“Schedule drifts”, especially on long-haul flights, may influence the arrival flow during
certain times of the day and the use of ATFM airport regulations might be necessary to
manage those occasional peaks of demand. Nevertheless, the systematic daily use of
- 34 -
01-12-04
01-11-04
01-10-04
01-09-04
01-08-04
01-07-04
01-06-04
01-05-04
01-04-04
01-03-04
01-02-04
01-01-04
01-12-03
01-11-03
01-10-03
01-09-03
01-08-03
01-07-03
01-06-03
01-05-03
01-04-03
01-03-03
01-02-03
300
05:00
01-01-03
360
06:00
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
ATC/Aerodrome capacity related ATFM regulations during the same time should not take
place at coordinated airports.
4.1.2.4.
Accuracy and cancellation of ATFM regulations
The use of ATFM airport arrival regulations as well as the applied parameters (magnitude
and duration of capacity drop) play an important role in avoiding unnecessary delays.
If conditions improve significantly, then regulations are usually cancelled. When ATFM
regulations are cancelled at short notice, flights which are already airborne, or are close to
their ATFM slot time, cannot avoid delays (see Figure 4-10). Furthermore, the airport that
issued the ATFM regulation might not be able to use a part of its available capacity until the
traffic demand is back to normal.
Departing flights from origin airports within EUROCONTROL area
~2hrs
ATFM regulation
Cancel time
before start
of regulation
Cancel time
after start of
regulation
Planned
start of
regulation
Planned End
of regulation
Figure 4-10: The impact of cancelled ATFM regulations on departing flights
Figure 4-11 shows that not only the number of regulations but also the frequency of
cancellations vary considerably from airport to airport. A large number of airport ATFM
arrival regulations are cancelled before their planned end time, typically between 1 and 3
hours before the scheduled end of the regulation, as shown in Figure 4-11. A significant
number of regulations were cancelled less than 2 hours before the planned start of the
regulation. By then, most regulated flights cannot avoid ATFM delays.
ATC/Aerodrome related ATFM regulations
cancelled less than 2hrs before start
cancelled more than 2 hrs before end
cancelled less than 2hrs before end
Not cancelled
ZRH
VIE
FCO
MXP
CDG/LBG*
-
MAD
-
BCN
200
AMS
200
LHR
400
MUC
600
400
ZRH
600
VIE
800
FCO
800
MXP
1 000
CDG/LBG*
1 000
MAD
1 200
BCN
1 200
AMS
1 400
LHR
1 400
MUC
1 600
FRA
1 600
Number of airport ATFM arrival regulations
1 800
FRA
Weather-related ATFM regulations
1 800
Figure 4-11: Cancelled airport ATFM arrival regulations
As far as ATC/Aerodrome related airport ATFM arrival regulations are concerned, the high
number of cancellations for some airports might be due to flow management strategy,
airport scheduling issues, genuine schedule drifts, inaccurate demand forecasts or
inappropriate use of ATFM regulations. For example, Milan Malpensa applies ATFM
- 35 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
regulations almost every day (see previous section), of which a very high percentage are
cancelled well before the anticipated end time.
The high number of cancellations of weather related airport ATFM arrival regulations at
some airports might be driven by insufficient integration of MET information in decisionmaking or a genuine difficulty to forecast weather phenomena. Munich airport for example
is close to the Alps and therefore exposed to sudden changes of weather conditions.
4.1.2.5.
Performance of ATFM regulations and quality assurance
As described in the previous sections, several factors influence the issuance of ATFM
regulations. This includes for example:
• airport scheduling;
• service parameters (quality of service);
• policy on and use of local flow management techniques (i.e. systematic or
exceptional use of holdings etc.);
• experience of ATC supervisor, flow manager; and,
• quality of information available when the decision has to be taken.
Currently, it is difficult to realistically determine if an ATFM regulation was the most
appropriate solution for a specific traffic scenario because not all relevant data are
systematically captured by the relevant stakeholders.
Furthermore, the use of local flow management measures (e.g. airborne holding) is usually
not known to the CFMU. Neither is the CFMU made aware when local flow measures are in
place to protect the airport. In order to make efficient and appropriate use of ATFM
regulations, there is clearly a need to find the sustainable balance between anticipated
airborne and ground delays in case of a capacity shortfall due to over deliveries or a
reduction of available airport capacity.
Extensive use of airborne holdings is costly for aircraft operators and has an environmental
impact. The measurement and comparison of airborne terminal holding performance would
be an important element in analysing operational air transport performance. However,
reliable data on terminal holdings are currently unavailable for most of Europe.
Airport ATFM regulations and the balance of ground and airborne delays have to be
systematically assessed through post-event analysis.
4.2.
Airline, airport and other causes
Local delays caused by airports, airlines, ground handlers or passengers are a large
contributor to the variability of departure times and need to be analysed in more detail.
However, as this report focuses on ATM related issues, a thorough analysis of the complex
and interrelated pre-departure processes is beyond the scope of this report. Only a brief
overview is given.
Figure 4-12 provides a high-level illustration of the many factors that may affect operations
before leaving the gate. In addition to non-scheduled maintenance or defects of aircraft
and/or airport facilities and equipment, a multitude of interrelated supporting processes for
flight departure need to be coordinated in order to work smoothly together.
- 36 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
On Block
Off Block
- 30 min.
Turn-around phase
Check-in
Deboarding
Preparation at gate for boarding
Boarding
Loading of cargo & luggage
Unloading of cargo & luggage
Crew briefings & flight preparations
Refuelling
Catering
Figure 4-12: Processes affecting air transport operations before departure
Due to the significant costs involved, many airlines and airports have working groups
dedicated to improving and optimising those processes. European Collaborative Decision
making (CDM) projects play also an important role as they strive to improve the way
airlines, airports and ATM work together at operational level (departures and arrivals)
through increased information exchange and improved automated decision support tools.
4.3.
Reactionary delays
Reactionary delays43 need to be better understood. Due to the interconnected nature of the
air transport system, long delays at a local bottleneck can cause a “snowball effect” that
propagates in the entire network.
Most reactionary delays are the result of long primary delays (including weather related
delays, technical failures, ATFM delays, etc.). Long delays tend to propagate longer
through the network, especially when long delays occur in the morning. This causes
disruptions to the scheduled flows all over Europe (schedule drifts). Figure 4-13 illustrates
the evolution of reactionary delay during the day in the European network.
The magnitude of the delay propagation effect on the air transport network depends on
many individual parameters such as scheduled block and turn-around times,
demand/capacity ratios at airports and boarding performance to name a few. For example,
if the scheduled turn-around time is close to the minimum turn-around time at an airport, a
primary delay is more likely to result in a reactionary delay on the next leg, and eventually
on connecting flights.
It was noted that reactionary delays mainly occur:
• on high density hub-to-hub connections;
• on early morning arrival waves from spoke airports; and,
• during bad weather situations.
The propagation of delay is an important dynamic factor, which affects the stability of the
overall network. One should consider whether more provisions should be introduced to
absorb reactionary delays or whether it is possible to implement efficient procedures to
reduce reactionary delays during the day (see Figure 4-13).
43
Reactionary delays are caused by the late arrival of aircraft or crew from previous journeys.
- 37 -
DRIVERS OF VARIABILITY BEFORE PUSH BACK
Punctuality drivers at major European airports
minutes of delay in 2004 (' 000)
2,500
2,000
1,500
1,000
500
0
4
5
6
7
8
9 10 11 12 13
Local (departure airport)
Local (arrival airport)
Reactionary
14 15 16 17
En-route
Other Causes
Please note that this chart only displays a selected CODA
sample which does not correspond to all European traffic
18
19
20
21
22
Data Source: eCODA
Figure 4-13: Distribution of departure delay by time of day
This figure illustrates that reactionary delays are driven by primary delays in early morning.
This is affected by the following primary delay drivers:
•
•
•
poor visibility conditions;
schedule drifting of long-haul flights which generate an excess of demand, and,
en-route ATFM delay
The apparent imbalance between airport capacity and demand in early morning, which
creates reactionary delays all through the day, should be further investigated.
ATM could generate added-value to air transport by limiting reactionary delays through a
number of measures including:
• Better management of bad weather situations (see Section 2.1.2);
• Better management of long haul flights in early morning (e.g. speed control of traffic
ahead of schedule several hours before arrival, required time of arrival);
• Improvement of airport scheduling process; and,
• Exploring the applicability of changing the priority rule for ATFM from “first-planned
first-served” to “first scheduled-first served”44 at coordinated airports to reduce the
propagation of delays. Both priority rules are equally equitable as neither favours a
specific airline;
• Further studies into the propagation of reactionary delays.
44
The “first scheduled” rule is used in the USA.
- 38 -
DRIVERS OF VARIABILITY AFTER PUSH BACK
Punctuality drivers at major European airports
5. DRIVERS OF VARIABILITY AFTER PUSH BACK
Before looking at more detail at the individual drivers of variability after the aircraft has left
the gate, it should be pointed out that, due to the nature of aviation, a certain level of
variability of operations is considered to be normal. This “natural” variability can be the
result of many influencing factors (weather, different runway configurations, pilot
performance, etc.). In this context, it is important to identify if and to what extent the drivers
of variability represent a problem and to isolate the ones which could realistically be
reduced.
Variability of flight operations: taxi times45
5.1.
Figure 5-1 shows the distribution of standard deviations for taxi-out and taxi-in times for
each flight-leg with 20 or more trips per month. This method is used to account for airline
specific gate allocations, congestion during certain times of the day, aircraft type and, in
some cases, for runway configuration (see also section 1.2).
A small variance of taxi times is a natural effect, depending on local taxi distances from
stand to runway. Figure 5-1 shows that while the distribution of taxi-in times is fairly tight
(with the exception of London Heathrow and Amsterdam46), the distribution of “time to take
off” is much wider at the analysed airports, introducing some variability and unpredictability
in the network.
0%
0%
ZRH
Grouping of standard deviation in minutes per monthly
scheduled service (more than 20 flights per month)
0-2.5
2.5-5
7.5-10
>10
ZRH
10%
VIE
10%
MXP
20%
MUC
20%
MAD
30%
LHR
30%
FRA
40%
FCO
40%
CDG
50%
AMS
50%
VIE
60%
MXP
60%
MUC
70%
MAD
70%
LHR
80%
FRA
80%
FCO
90%
CDG
90%
BCN
100%
AMS
100%
BCN
"Taxi in time" variations 2004
"Time to take off" variations 2004
5-7.5
Figure 5-1: Standard deviation of taxi times at the 11 airports (2004)
The “time to take off” seems to be least predictable at London Heathrow, Rome Fiumicino,
Paris Charles de Gaulle and Madrid. Good levels of predictability are observed at Zurich,
Frankfurt and Vienna.
45
46
Taxi times include time spent waiting for a gate at the arrival end of the flight and the time waiting to take
off. It is important to note that no attempt is made to determine the cause of delay.
At Amsterdam airport the observed variation might be due to the new runway which doubles taxi times
when a change of runway configuration is required. At London Heathrow airport the variations in taxi-in
times are likely to be due to congestion in the terminal area.
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DRIVERS OF VARIABILITY AFTER PUSH BACK
Punctuality drivers at major European airports
It would be important to understand the drivers of taxi time variability. Detailed analysis
carried out by the individual airport communities and sharing best practice with other
communities can potentially reduce the variability of taxi times.
High variability in the “time to take off” can affect the effectiveness of ATFM regulations.
Aircraft subject to ATFM regulations are supposed to take-off within a given window (-5,+10
minutes) around the assigned ATFM slot. Compliance with this slot is difficult to achieve
when there is already a queue of aircraft waiting for take-off. It would be worth examining if
take-off times could be better controlled using departure management tools and processes.
Furthermore, in the CFMU system, taxi times are considered as fixed values for the flight
progress calculation. As shown above, there can be significant variations in the time to take
off and the fixed values used in the CFMU system for the calculation of flight progress
might produce inaccurate data. However, it should be pointed out that a better integration
of more accurate taxi times in the CFMU system would improve the system significantly but
it would not reduce variability of taxi times as such.
5.2.
Variability of flight operations: airborne times
Variations in flight times can be broken down into en-route and terminal transit times.
5.2.1. Variations in en-route transit times
Whereas there are quite significant variations in en-route transit times for long haul flights
(jet stream, more direct routing during off peak times), there is only moderate variation in
en-route transit times on intra-European flights [Ref.ii]
At some airports, the varying arrival times of long haul flights can represent a real problem,
as those flights cannot be controlled by ATFM regulations. For example, major hubs such
as Frankfurt and London Heathrow are often subject to schedule drifts. Long-haul traffic
arrives in the morning with a tolerance of approximately ±25 minutes (dependent on jet
stream and routing), which might require intensive application of wake vortex separations
and consequently reduce the available arrival capacity. If such schedule drifts of long haul
traffic is experienced when arrival capacity is already reduced due to bad weather (i.e. fog
in the morning), airports might have to issue an ATFM airport arrival regulation to restrict
the European traffic flow.
5.2.2. Variations in en-terminal transit times
Airborne holding appears to vary significantly among airports. Airborne terminal holdings
appear to vary significantly among airports. It was not possible to analyse this in depth,
however, as the requisite data are only publicly available for London airports. This lack of
data represents a serious limitation when doing the post analysis in preparation for the next
season.
UK NATS however publishes relevant information in its monthly performance bulletins.
Figure 5-2 shows holding times for flights into London Heathrow in September 2004 as an
example of information that would be expected from major airports on a regular basis.
- 40 -
DRIVERS OF VARIABILITY AFTER PUSH BACK
Monthly
hold
timeArrivals
and arrivals
(Sep. 2004)
Hold
Time
And
By Hour
of Day
Aircraft
Average
AverageHold
holdTime
time
22
20
18
16
14
12
10
8
6
4
4000
2624
2000
253
12
1
0
60+
2
6000
50-60
Average Hold Time
Average
hold time
7352
8000
20-30
Arriving aircraft
9683
10000
10-20
Hour of day
Arriving Aircraft
Distribution Delay
12000
0-10
0
16
14
12
10
8
6
4
2
0
40-50
1600
1400
1200
1000
800
600
400
200
0
30-40
Arriving
Aircraftarrivals
Hold time
and monthly
Punctuality drivers at major European airports
Time Held
Source: NATS
Figure 5-2: Holding time into London Heathrow (September 2004)
Beside improvements in punctuality and flight time savings, there would be significant
environmental benefits (reduced noise, emissions and fuel burn) if holding in terminal areas
could be reduced by more accurate flow control into airports. One option might be the
introduction of en-route sequencing, which is currently not applied in Europe.
- 41 -
42
CONCLUSIONS
Punctuality drivers at major European airports
6. CONCLUSIONS
This report is a first attempt to establish a link between air transport, airport and Air Traffic
Management (ATM) performance, at the initiative of EUROCONTROL’s Performance
Review Commission (PRC). It identifies and measures an initial set of air transport
punctuality drivers at major European airports, seen from an ATM perspective. The eleven
airports are: Amsterdam Schiphol, Barcelona, Paris Charles de Gaulle, Rome Fiumicino,
Frankfurt, London Heathrow, Madrid, Munich, Milan Malpensa, Vienna and Zurich.
This report was prepared and validated in interaction with the airport communities
concerned, i.e. airport authorities, airlines and ATM at those airports. This interaction with
airport communities proved to be very fruitful and hopefully results in high added-value for
everyone. In addition, the report’s preliminary findings and conclusions were discussed at a
workshop held in open forum on 20 April 2005, at which there was a representative crosssample of interested parties.
The Performance Review Unit gratefully acknowledges the contributions received from
everyone concerned.
The underlying analysis was made possible by the recent availability of punctuality data
from EUROCONTROL’s Central Office for Delay Analysis (CODA), covering now more
than 50% of scheduled flights and by linking this data with data from the EUROCONTROL
Central Flow Management Unit (CFMU).
• The continued availability of such data will be essential to extract the high potential
value of this database for individual parties and for the wider interest of air transport
policy.
• Many parties could benefit from controlled access to the CODA information.
EUROCONTROL should identify with interested parties what services it
could/should offer in this respect, e.g. standard queries through the Internet.
• Punctuality and related delay causes could be measured in a uniform way. Local
and network drivers could be distinguished.
Beyond measuring punctuality and understanding underlying delay causes, the variability
of flight operations emerged as an important issue towards improving air transport
performance. A reduction of variability directly translates into improved punctuality and/or
reduced costs to meet the same punctuality target. The PRC’s eighth Performance Review
Report (PRR 8) states that compressing half of flight schedules by five minutes would be
worth some € 1000 million per annum.
The report measures the “variability of flight operations” globally, per airport and in the
different phases of flight. It attempts to trace the variability in arrival delays to variability in
departure time, “time-to-take-off”, flight time and taxi-in. It identifies the following as
significant drivers of “variability of flight operations”:
• Airport and airline scheduling processes;
• the management of bad weather at European airports;
• flow management strategies into airports. Observed cases of daily ATFM airport
arrival regulations to address predictable excess demand at airports are a signal of
airport scheduling issues and/or inadequate use of ATFM regulations. ATFM/airport
quality control should monitor this issue on an ongoing basis, with visibility for all
concerned stakeholders;
• Management of long haul flights bound for Europe.
The study also gives some clues as to the propagation of delays from flight to flight, and
hence as to ways to improve reactionary delays.
- 43 -
CONCLUSIONS
Punctuality drivers at major European airports
This report remains mostly descriptive. More work is needed to extract the full value of the
new field it opens. It does however point to many possible improvements in airline, airport,
ATM and ATFM operations, and in their interaction through e.g. Collaborative Decision
Making (CDM), which warrants further action by the EUROCONTROL Organisation and
others. For its part, the PRC will endeavour to reach more definitive conclusions and to
build recommendations on the basis of this further work.
- 44 -
POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY
Punctuality drivers at major European airports
7. POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY
The report attempts to establish a link between air transport, airport and air traffic
management performance and raises many issues which should be further explored with a
view to improving air transport punctuality in Europe. During the workshop held on 20 April
2005, it became clear that further action is needed at local level by the individual airport
communities. Action is also needed at European level by the EUROCONTROL
Organisation, and possibly by the European Commission.
The need for a cultural change to a more proactive, transparent, no-blame management of
air transport operations was highlighted during the workshop. Airlines, airports and the ATC
and ATFM community need to move from an “insular perspective” to a more general focus
on overall air transport performance. At local level, this means that the entire airport
community should work closely together in order to develop a common understanding of
objectives, which includes mutually agreed and clearly defined measurable targets.
Building on this report, key drivers of air transport performance need to be further analysed
and appropriate. Comparable indicators need to be developed at local and network level for
continuous performance monitoring.
Broadly, the areas of action can be grouped according to their origin (local airport
community/ network) and their nature (strategic/tactical), as shown in Figure 7-1.
Collaborative
Decision Making
(CDM)
Cultural
change
Strategic and tactical
network issues
(to be addressed by
transnational working
groups)
Data availability and
quality to clearly
identify the main
drivers of air
transport variability
Sharing of
Best practice
Strategic and tactical
local issues
(to be addressed by
airport community)
Proactive air traffic
management
Figure 7-1: Action areas for improving air transport punctuality
Data access and quality are the key to developing a comprehensive performance
measurement framework. CFMU and CODA data provide essential information for
progress in analysing air transport performance at European and at airport level. Reporting
into CODA should be further improved for a comprehensive coverage of scheduled flights
and delay causes, possibly under EC rules, and to enable analysis from a network
perspective to be conducted. Moreover, data quality and accessibility for the comparison of
terminal holding times should be improved in order to get a clearer understanding of
variability in the terminal transit times.
- 45 -
POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY
Punctuality drivers at major European airports
7.1.
Network issues
7.1.1. Establish a better understanding of “network effects”
Network effects and reactionary delay need to be better understood. Despite the large
share of reactionary delay, there is currently only a limited knowledge on how individual
airline (scheduling of block and turn around times) or airport strategies (airport scheduling,
use of ATFM regulations, demand capacity ratios) affect the air transport network.
Most reactionary delays are the result of long primary delays, especially when those delays
occur in the morning. It appears that the European air transportation network is not able nor
has the contingencies to absorb or reduce reactionary delays during the day.
7.1.2. Post event analysis of ATFM performance
Consideration should be given by the CFMU to extending its procedures for the
management of critical events (e.g. bad weather) and post-event analysis of ATFM
performance, with involvement of all concerned parties. Overly penalising regulations for
flights with a flying time of 2-3 hours should be reviewed.
A first important step would be the obligatory recording of the actual demand situation
when an ATFM regulation is issued by the FMP. This would enable ex-post analysis and
form the basis for a quality management system for ATFM regulations. This would benefit
the whole European air transport system. Alternative options could be explored by all
involved parties when a systematic use of ATFM regulations is identified.
In the US, post operations evaluation tools and associated data are available to any user.
to explore a variety of standardised performance metrics including departure, en-route and
arrival delays. The tools offer powerful data mining capabilities to assist the user in
recognising patterns and trends. Some of the patterns currently recognised include circular
airborne holding, arrival fix swaps, and flown routes that differ significantly from the routes
filed. Another tool enables users to assess the performance of Ground Delay Programs
(GDP), which are similar to the European ATFM delay programme. Performance reports
show whether the GDP is delivering the requested rate and indicate why the desired rate is
not being achieved. A post analysis component allows for in-depth analysis after a GDP
has terminated. It provides GDP performance metrics and trend analysis features, which
compares the current GDP against past GDPs, allowing the user to identify patterns or
anomalies.
7.1.3. Introduction of a “serve by schedule” bias
In order to reduce variations against schedule, it would be interesting to explore to what
extent a modification of the rule of ATFM priority could help improving overall punctuality
whilst reducing the amount of reactionary delay, provided that safety is maintained
With radar data provided by UK NATS, BAA modelled a simple process by which the ICAO
rule of "First Come - First Served" was biased to give a preference to on-schedule
operation. illustrates the outcome from one day's operations, which was typical of
outcomes observed for the sample week.
This "Serve-by-Schedule" procedure (which is applied in the US) permitted the controller to
sequence aircraft from the stacks with a preference toward on-schedule operation. This
discretion was constrained to limit the delay of any one aircraft to a specified maximum
holding in the stack. A period of 25 minutes was assumed for this example. The outcome
was that, while the total terminal holding time remained unchanged, on-schedule and
delayed aircraft experienced less terminal holding at the expense of flights that arrived prior
to their schedule. This improved the punctuality on the airport at zero overall cost.
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POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY
Punctuality drivers at major European airports
Furthermore, such an approach might have the potential to reduce reactionary delay as
already delayed aircraft experience less additional delay in the terminal holding area.
Actual situation observed during a
„normal“ day (ICAO rules)
Total of 86
hours of
on block delay
=
„lateness“
plus
holding
Situation based on radar data
(holdings based on first scheduled
first served criteria)
A/c late on-block
with late arrival at
LHR plus airborne
holdings
22 hrs.
64 hrs.
Early arrivals
on block before
schedule - even
with holding
55 hrs.
28 hrs.
Total of 55
hours
on-block
earliness
=
“earliness”
minus
holding
Total of 72
8 hrs.
hours of
on-block delay
=
64 hrs.
„lateness“
plus holding
Longer holdings for
early arrivals, but
closer to schedule
when on-block
• Aircraft operating to schedule get affected by early
arrivals and suffer from holdings (+22 hours);
• Punctuality of early arrivals improves as they get
affected by holdings (+28 hrs)
Shorter holdings
for
delayed arrivals
thus nearer to
scheduled on-block
time
41 hrs.
42 hrs.
41 Hours
hours of
actual
„earliness“
=
„earliness“
minus
holding
• Longer holdings for early arrivals improve
punctuality;
• Reduction of holding for aircraft arriving late;
Holding in the Stack
Data source: BAA
Figure 7-2: Rule of ATFM priority
7.1.4. En-route sequencing
More continuous and accurate delivery of arrival flows from the network has the potential to
improve flight efficiency and environmental friendliness in terminal areas. It offers the
possibility to make better use of airport capacity and, consequently, to compress airline
schedules thanks to reduced variability of operations. As pointed out in paragraph 2.4.1 in
Chapter 2, there is currently no en route sequencing in Europe. For example, it should be
explored to what extent en-route speed control with required time of arrival (RTA) could
help reducing schedule drifts on long haul transatlantic flights47, provided they are applied
well in advance.
Genuine en route sequencing is practised in the US where it is called Miles in Trail (MIT)
and it should be explored to what extent some measures of en-route sequencing would be
beneficial of European air transport operations.
7.2.
Local airport community issues
7.2.1. Airport capacity declaration and slot allocation
As already pointed out in the report, there appears to be scope for improvement of the
airport capacity declaration process and the consecutive airport slot allocation process at
some airports. As shown by the Frankfurt airport community, de-peaking during the critical
hours of the day can provide substantial benefits if all parties are included in the process.
47
Transatlantic traffic is not affected by ATFM regulations as the departure airports are not in the
EUROCONTROL area. Some flights from departure airports outside the CFMU area may be subject to
ATFM slot allocation.
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POSSIBLE ACTION AREAS FOR IMPROVING AIR TRANSPORT PUNCTUALITY
Punctuality drivers at major European airports
Additional information from the slot user could also prove beneficial for the airport capacity
declaration process. At the moment, once a slot has been declared, it can be used by any
type of aircraft (heavy to light wake vortex) to any destination by the slot owner. Hence, the
exact traffic mix and preferential departure routes are not known to the airport operators at
the scheduling stage.
7.2.2. Collaborative Decision Making Programmes
Collaborative Decision Making (CDM) should be further promoted and applied for arrival,
turn-around and departure phase. For example, knowledge transfer and consultation
between FMP, local ATC and airport before an ATFM airport regulation is issued might
help reducing ATFM related delays.
7.2.3. Improved sustainability of airport arrival capacity during bad weather
Airport communities should strive to minimise the gap between declared peak arrival
capacity and actual experienced arrival capacity due to bad weather. Better integration of
MET expertise in the ATFM/ATC decision-making process offers substantial benefits. An
interesting experience can be observed at Amsterdam Schiphol Airport where LVNL (ATC),
KNMI (MET provider), KLM and the airport authority jointly developed a tool to establish the
probability of a capacity reduction at AMS airport on the next operational day. The key idea
is to make optimum use of available capacity by enabling the respective parties to plan for
the most likely scenario.
There appear to be considerable differences between airports regarding procedures
applied during bad weather conditions (separation minima on final approach at reduced
visibility, acceptable crosswind values, etc). Airport communities should be encouraged to
identify and share best practice procedures.
Moreover, the feasibility and economic viability of MLS and time based sequencing tools
should be further explored and results should be shared with all interested parties.
7.2.4. Controlling arrival flows into airports
ATFM regulations are not a suitable to “fine-tune” arrival flows as they are implemented
several hours in advance and only achieve an accuracy in the order of 5 to 10 minutes. In
contrast, airborne techniques such as linear and circular holdings are usually available at
short notice and can therefore target small excesses in demand effectively with minimal
capacity wastage.
The optimum solution appears to be a strategy which combines and balances the following
techniques in order to enhance the quality of the arrival flow into airports:
•
•
•
•
realistic airport scheduling (and de-peaking of schedules if necessary) to ensure
that the mean traffic flow does not exceed the airport departure and arrival
capacities, hence avoiding delays built-in to schedules (see also previous section);
ATFM take-off slots (15 minutes wide) in exceptional cases, when there is a
significant imbalance between demand and available capacity;
en-route flight sequencing in the tactical phase (ATC delivery accuracy better than 1
minute); and,
local sequencing tools such as vectoring/ holding to smooth the residual variance.
Well balanced airport strategies combined with a continuous, pre-sequenced high quality
arrival flow have the potential to reduce ground delays to nearly zero in normal conditions.
Traffic flow peaks and troughs would be balanced principally at high altitude and only
marginally the terminal area. This would be less costly in fuel burn and environmental
impact than holding at low altitude. Further work is also required in order to find strategies,
which balance economic and environmental interests.
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8. GLOSSARY
ACC
Area Control Centre
AEA
Association of European Airlines
AIP
Aeronautical Information Publication
Airport Slot
The permission given by a coordinator in accordance with EC Regulation 793/2004 to use
the full range of airport infrastructure necessary to operate an air service at a coordinated
airport on a specific date and time for the purpose of landing or take-off as allocated by a
coordinator.
AMS
Amsterdam Airport Schiphol, The Netherlands
ANM
ATFM Notification Message
ANS
Air Navigation Service. A generic term describing the totality of services provided in order
to ensure the safety, regularity and efficiency of air navigation and the appropriate
functioning of the air navigation system.
ANSP
Air Navigation Services Provider
ATC
Air Traffic Control. A service operated by the appropriate authority to promote the safe,
orderly and expeditious flow of air traffic.
ATCO
Air Traffic Controller
ATCSCC
Air Traffic Control System Command Centre
ATFCM
Air Traffic Flow and Capacity Management
ATFM
Air Traffic Flow Management. ATFM is established to support ATC in ensuring an optimum
flow of traffic to, from, through or within defined areas during times when demand exceeds,
or is expected to exceed, the available capacity of the ATC system, including relevant
aerodromes.
SES definition: “A function established with the objective of contributing to a safe, orderly
and expeditious flow of air traffic by ensuring that ATC capacity is utilised to the maximum
extent possible, and that the traffic volume is compatible with the capacities declared by
the appropriate air traffic service providers”.
ATFM delay (CFMU)
The duration between the last Take-Off time requested by the aircraft operator and the
Take-Off slot given by the CFMU
ATFM measure
Refers to all type of flow management measures (e.g. level-capping etc).
ATFM regulations
Refers to ATFM measures which hold the aircraft at the airport of departure.
ATM
Air Traffic Management. A system consisting of a ground part and an air part, both of which
are needed to ensure the safe and efficient movement of aircraft during all phases of
operation. The airborne part of ATM consists of the functional capability which interacts
with the ground part to attain the general objectives of ATM. The ground part of ATM
comprises the functions of Air Traffic Services (ATS), Airspace Management (ASM) and Air
Traffic Flow Management (ATFM). Air traffic services are the primary components of ATM.
AUP
Airspace Use Plan
Bad weather
For the purpose of this report, “bad weather” is defined as any weather condition (e.g.
strong wind, low visibility, snow) which causes a significant drop in the available airport
capacity.
BCN
Barcelona Airport, Spain
Block time
The time between off-block at the departure airport and on-block at the destination airport
CAA
Civil Aviation Authority
CASA
Computer Allocated Slot Allocation
CDG
Paris Charles de Gaulle Airport, France
CDM
Collaborative Decision Making. http://www.euro-cdm.org/
CFMU
EUROCONTROL Central Flow Management Unit
CODA
EUROCONTROL Central Office for Delay Analysis
Any airport where, in order to land or take-off, it is necessary for an air carrier or any other
aircraft operator to have been allocated a slot by a coordinator, with the exception of State
flights, emergency landings and humanitarian flights.
Capacity Prognosis tool developed at Amsterdam airport Schiphol
Co-ordinated airport
CPS
- 49 -
CTOT
Calculated Take-Off Time
EAW
Early Access to Weekend Routes
eCODA
Enhanced Central Office for Delay Analysis (EUROCONTROL)
EC
European Commission
EOBT
Estimated Off Block Time
ESP
En-route Spacing Program
ETA
Estimated Time of Arrival
ETFMS
Enhanced Tactical Flow Management System
EUROCONTROL
The European Organisation for the Safety of Air Navigation. It comprises Member States
and the Agency
FAA
Federal Aviation Administration, United States
FAP
Future ATM Profile
FCO
Rome Fiumicino Airport, Italy
FIR
Flight Information Region. An airspace of defined dimensions within which flight
informantion service and alerting service are provided
FMP
Flow Management Position
FPL
Filed Flight Plan
FRA
Frankfurt Airport, Germany
FSA
Flight Schedule Analyzer
GDP
Ground Delay Program (US)
IATA
International Air Transport Association
IFR
Instrument Flight Rules. Properly equipped aircraft are allowed to fly under bad weather
conditions following instrument flight rules
ILS
Instrument Landing System
KPI
Key Performance Indicator
LHR
London Heathrow Airport, United Kingdom
LVNL
Luchtverkeersleiding Nederland, ANS Provider in The Netherlands
MAD
Madrid Barajas Airport, Spain
MET
Meteorology
MIT
Miles in Trail
MLS
Microwave Landing System
MUC
Munich Airport, Germany
MXP
Milan Malpensa Airport, Italy
NATS
National Air Traffic Services, ANS Provider in United Kingdom
POET
Post operations Evaluation Tool
PRC
Performance Review Commission
Primary delay
The result of initial delays caused to a given flight. Delay causes are usually grouped into
categories such as weather, ATC, etc
PRR
Performance Review Report
PRU
Performance Review Unit
Punctuality
The proportion of flights delayed by more than 15 minutes compared to published
departure and arrival times (off-block / on-block versus scheduled times)
RAD
Route Availability Document
Reactionary delay
Delay caused by the late arrival of aircraft or crew from previous journeys
RNDSG
Route Network Development Sub-Group
RPL
Repetitive Flight Plan
RTA
Requested Time of Arrival
Schedule drifts
Is the difference between the actual and scheduled arrival or departure times, which may
be caused by a number of reasons (e.g. weather, technical problems, ATFM reasons).
Separation minima
Separation Minima is the minimum required distance between aircraft. Vertically usually
- 50 -
1000 ft below flight level 290, 2000 ft above flight level 290. Horizontally, depending on the
radar, 3NM or more. In the absence of radars horizontal separation is achieved through
time separation (e.g. 15 minutes between passing a certain navigation point).
Slot (ATFM)
A time window assigned to an IFR flight for ATFM purposes
STATFOR
Specialist Panel on Air Traffic Statistics and Forecast
Taxi-in
For the purpose of this report, the time from touch-down to arrival block time
Taxi-out
For the purpose of this report, the time from off-block to take-off, including eventual holding
before take-off
TMA
Terminal Management Area
TWR
Traffic Controlled Tower
UK
United Kingdom
US
United States of America
VFR
Visual Flight Rules. Under clear weather conditions (VMC), aircraft are allowed to fly using
visual navigation. Most small aircraft use visual navigation as they do not have proper
equipment to permit IFR navigation.
VIE
Vienna Airport, Austria
ZRH
Zurich Airport, Switzerland
- 51 -
9. REFERENCES
i
University of Westminster “Evaluating the true cost to airlines of one minute of airborne or
ground delay” (2004), http://www.eurocontrol.int/prc/index.html.
ii
Performance Review Commission, Seventh Performance Review Report (PRR 7), An
assessment of Air Traffic Management in Europe during the calendar year 2003 (April
2004), http://www.eurocontrol.int/prc/index.html.
iii
Council Regulation (EC) No 95/93 of 18 January 1993 on common rules for the allocation of
slots at Community airports Official Journal L 014 , 22/01/1993 P. 0001 – 0006.
iv
Regulation (EC) No 793/2004 of the European Parliament and of the Council of 21 April
2004 amending Council Regulation (EEC) No 95/93 on common rules for the allocation of
slots at Community airports Official Journal L 138 , 30/04/2004 P. 0050 - 0060
v
Performance Review Commission, Eighth Performance Review Report (PRR 8), An
assessment of Air Traffic Management in Europe during the calendar year 2004 (April
2005), http://www.eurocontrol.int/prc/index.html.
vi
CFMU Operations Executive Summary – Edition 2002.
vii
IATA Worldwide Scheduling Guidelines, 10th Edition, Effective 1 July 2004.
viii
The Institute of Economic Affairs, “A market in airport slots”, London 2003.
ix
UK NATS, “A guide to runway capacity”, 2003.
x
EUROCONTROL, “Tasking Support for the consistency between airport slots, FPL and
ATFM slots”, 2004.
- 52 -
© European Organisation for the Safety of Air Navigation (EUROCONTROL)
EUROCONTROL, 96, rue de la Fusée, B-1130 Brussels, Belgium
http://www.eurocontrol.int
This document is published in the interest of the exchange of information and may be copied in whole or in part providing that the copyright notice and disclaimer are included. The information contained in this document may not be modified without prior written permission from the Performance Review Unit.
The views expressed herein do not necessarily reflect the official views or policy of EUROCONTROL, which makes no warranty, either
implied or express, for the information contained in this document, neither does it assume any legal liability or responsibility for the
accuracy, completeness or usefulness of this information.