Punctuality Statistics Notes

Punctuality Statistics Notes

Estimated release dates (updated 24 April 2015)
 
 Data Month Date Available On Website
 January 2015 28/04/2015
 February 2015 30/04/2015
 March 2015 23/05/2015
 April 2015 23/06/2015
 May 2015 21/07/2015
 June 2015 20/08/2015
 July 2015 23/09/2015
 August 2015 22/09/2015
 September 2015 20/11/2015
 October 2015 22/12/2015
 November 2015 25/01/2016
 December 2015 22/02/2016
 Annual 2015 Week Commencing 21/03/2016

 

Notes on CAA Punctuality Statistics (revised 24 April 2015)

1.   CAA statistics on punctuality are compiled by the Civil Aviation Authority with the co-operation of airports and Airport Co-ordination Ltd, and    currently cover passenger flights at 24 UK airports. 

 

2.   On-time performance and delay are calculated from the scheduled on-stand time (provided by Airport Co-ordination Ltd.), the reported runway time (provided by the airport) and the expected time an aircraft takes to travel between a stand and the runway (this taxi time is estimated using historic data – see note 12).

 

3.   An ‘on-time’ flight is defined as departing or arriving at a UK airport either early or up to and including 15 minutes late. 

 

4.   Average delay is the total minutes of delay recorded by all flights (with early arriving flights counted as zero delay) divided by the total number of flights monitored.

 

5.   Delay is recorded as the difference between an aircraft's scheduled and actual arrival or departure time at the airport terminal. It does not therefore measure any delay, such as that due to congestion, which has already been allowed for in the planned flight times of the service. Delays can occur for a variety of reasons. Operating circumstances, both within and without the airline’s control, also vary by route and by type of service.

 

6.   The statistics cover only those flights which were operated; they do not cover those flights which were cancelled. Some airport or airline business models prioritise delaying flights rather than cancelling them outright.

 

7.   The characteristics of scheduled and charter modes are different. For example, scheduled and charter flights tend to operate to different destinations at different times of the day and week. Because of this and the exclusion of cancellations from the data, simplistic comparisons between the two modes should be avoided.  These tables are not intended and should not be treated as a direct comparison between scheduled and charter services.

 

8.   Actual times of operation are derived from the flight by flight air transport movement returns made by airports to the CAA, which are compared with planned arrival and departure times supplied by Airport Co-ordination Ltd. The data supplied by Airport Co-ordination Ltd includes changes made up to 30 minutes before operation.

 

9.   When the two sets of data are matched, if an airline appears to operate a series of flights significantly “off slot”, the CAA will substitute information from published timetables (where such are available) in place of the Airport Co-ordination Ltd slot data. Other mismatches between the two data sources are reconciled where appropriate through manual validation.

 

10. The number of unmatched actual flights represented those Air Transport Movements which were reported by the airport but for which no corresponding planned flight was found. The reasons for this would normally be: (a) the flight was a diversion from another airport; (b) the flight was not recorded with Airport Coordination Ltd or airport; (c) the flight was a short-haul flight more than one hour before the planned time; (d) the flight was planned to take place in the previous month; (e) the plan or the air transport movement record contained an incorrectly reported item of data causing the flight not to match.

 

11. The number of unmatched planned flights represents those flights planned for which a corresponding Air Transport Movement has not been found. The reasons for these would normally be: (a) the flight was diverted to another airport; (b) the flight was cancelled; (c) the planned time was for a short haul flight more than one hour after the flight; (d) the flight took place in the following month; (e) either the plan or the air transport movement record contained an incorrectly reported item of data causing it not to match.

 

12. Because the planned time of operation relates to the arrival/departure at the stand, whilst the actual time of operation relates to wheels on/off the runway, taxi time assumptions as per table below have been built in following information provided by Airport Coordination Ltd or the airport:

 

a.     Airports reported prior to quarter 4 2014:  A general review of taxi times was undertaken during 2008 and the amended values were implemented with effect from January 2009. For comparison purposes 2008 data, shown in 2009 tables, have been recalculated using new taxi times.

b.     Airports commencing reporting quarter 4 2014 (experimental): January and June 2013 data has been used to estimate taxi times, except for Exeter where November 2014 data has been used. 

Airport

Data from

Taxiing Time (Minutes)

Status

Notes

 

 

Arrivals

Departures

 

 

Aberdeen

October 2013

6

7

Experimental

 (iv)

Belfast City

October 2013

7

6

Experimental

 

Belfast International

October 2013

0

0

Experimental

(iii)

Birmingham

April 1989

0

0

 

(iii)

Bournemouth

October 2013

6

7

Experimental

 

Bristol

October 2013

7

7

Experimental

 

Cardiff

October 2013

9

5

Experimental

 

Doncaster Sheffield

October 2013

7

7

Experimental

 

Durham Tees Valley

October 2013

6

5

Experimental

 

East Midlands

October 2013

8

8

Experimental

 

Edinburgh

April 1996

8

10

 

 

Exeter

November 2014

8

10

Experimental

 

Gatwick

April 1989

10

17

 

(i), (ii)

Glasgow

July 1993

7

10

 

 

Heathrow

April 1989

10

25

 

(i)

Jersey

October 2013

8

3

Experimental

 

Leeds Bradford

October 2013

7

11

Experimental

 

Liverpool

October 2013

10

6

Experimental

 

London City

April 1997

3

15

 

 

Luton

April 1989

6

12

 

 

Manchester

April 1989

11

15

 

(i)

Newcastle

April 1996

5

8

 

 

Southampton

October 2013

7

9

Experimental

 

Stansted

April 1989

10

13

 

 

 

(i)             No account is taken of the different taxi-ing times associated with the terminal building used.

(ii)            Prior to October 2003, Gatwick recorded the departure time from the stand.

(iii)           Birmingham and Belfast International airports record actual time of operation as arrival / departure at the stand.

(iv)           All flights to oil rig destinations, and charter flights to Scatsta and Sumburgh have been excluded from Aberdeen data, as a significant proportion are sole use flights which may be subject to revision at short notice with no impact on general passengers

 

13. The use of average taxi times is sufficient for calculating an aggregate level of on-time performance, but would not be suitable for reviewing the punctuality of an individual flight.

 

14. The status of “experimental” is assigned to new data series which are not yet established. In this instance, it reflects the relative lack of historical comparative data and the estimation required for the taxi-time adjustment. In particular, users should recognise that greater variability in traffic volumes over time may increase the uncertainty around estimates made. 

 

15. With effect from January 2000, early flights are set to zero delay. Prior to this, an early flight will show a negative delay. This will affect the ‘average delay’ column. Average delays from January 2000 onwards should not be compared to average delays prior to January 2000. Tables for January to December 2000 inclusive do not include columns relating to the corresponding month the previous year for this reason. These tables should also not be compared with previously published tables.

 

16. Prior to April 1998, Luton planned times of operation were taken from daily flight plans provided by the airport. These were completed before the week in question and, therefore, did not reflect any changes to the plan made at short notice.

 

17. Route and airline combinations are shown where there is more than one matched flight. Any lines omitted for this reason will still be included in total figures however. For this reason, the totals shown may not always exactly match the data in the table.

 

18. All-cargo services and air taxi services are excluded from the analysis.

 

19. The CAA is the UK's specialist aviation regulator. Its regulatory activities range from making sure that the aviation industry meets the highest technical and operational safety standards to preventing holidaymakers from being stranded abroad or losing money because of tour operator insolvency.

 

20. The information contained in this report has been compiled from various sources and it is not possible for the CAA to verify whether it is accurate, nor does the CAA undertake to do so. Consequently, the CAA cannot accept any liability for any financial loss caused by any person's reliance on it.

 

21. Punctuality data are published monthly and annually in summary and in full on the CAA website: www.caa.co.uk/punctuality. For data queries please contact one of our analysts at the Civil Aviation Authority, Aviation Intelligence, K4, CAA House, 45-59 Kingsway, London WC2B 6TE, telephone 020 7453 6245.