Central Statistics Office, Ireland

Aviation Methodology and Quality Information

Direcorate Business Statistics - Transport Unit

Transport Section, Central Statistics Office, Skehard Road, Cork, Ireland

Aviation statistics are compiled from data supplied by all Irish airports. The following Irish airports provide data to the Central Statistics Office: Dublin, Cork, Shannon, Kerry, Knock, Connemara, Donegal and Inishmore. Galway and Sligo airports ceased operations in 2011. There have been no commercial flights in Waterford Airport since June 2016. Data for the five main Irish airports (Cork, Dublin, Kerry, Knock and Shannon) is supplied on a monthly basis. Data for regional airports (Connemara, Donegal and Inishmore) is supplied annually to the Central Statistics Office.

The data file that is received monthly/quarterly from the main Irish airports contains the following variables for each airport:

• Reporting airport
• Partner airport
• Direction
• Scheduled or non-scheduled
• Passenger or Freight/mail flight
• Airline
• Aircraft
• Passenger numbers
• Freight/mail loaded and unloaded
• Number of commercial flights
• Seat numbers
• Total number of aircraft movements.

The current series of Aviation Statistics was first collected in 2004. The data is collected from all Irish airports and transmitted to Eurostat. An Aviation release was first published in 2014 to make the data more accessible to users. The aviation statistics release provides information on the number of passengers and freight/mail handled by all main Irish airports categorised as follows:

• Airport
• Arrivals and departures for both passengers and freight/mail
• Type of travel and traffic (i.e. national or international) for both passengers and freight/mail
• Scheduled and non-scheduled flights for both passengers and freight/mail
• Country of flight stage origin and destination
• Top 10 airports for arrivals and departures of passengers for the five main Irish airports

In addition, details of the numbers of flights handled by all airports classified by arrivals/departures, national and international traffic and scheduled and unscheduled are provided. Data freight/mail carried is given for the five main airports classified by arrivals and departures and national and international flights.

Main airport: A main airport is defined as an airport through which in excess of 150,000 passengers fly per annum. The five main airports in Ireland are Dublin, Cork, Shannon, Knock and Kerry.

Regional airport: A regional airport is defined as an airport through which less than 150,000 passengers fly per annum. The three regional airports in Ireland are Donegal, Connemara and Inishmore.

Three data sets required by the Regulation – A1, B1 and C1 – are provided to Eurostat:

Dataset A1 - Flight Stage dataset : flight stage data registered for airport-to-airport routes, and broken down by arrivals/departures, scheduled/non-scheduled, passenger service/all-freight and mail service, airline information and aircraft type. The values provided concern passengers on board, freight and mail on board, commercial air flights as well as passenger seats available.

Dataset B1 - On Flight Origin/Destination dataset : flight stage data registered for airport-to-airport routes, and broken down by arrivals/departures, scheduled/non scheduled, passenger service/all-freight and mail service and airline information. The values provided concern passengers carried and freight and mail loaded or unloaded.

Dataset C1 - Airport dataset: airport data registered for declaring airports, and broken down by airline information. The values provided concern total passengers carried, total direct transit passengers, total transfer (indirect transit) passengers, total freight and mail loaded or unloaded, total commercial aircraft movements and total aircraft movements.

Data sets A1 and B1 are provided on monthly basis, while data set C1 is provided on annual basis.

Airports handling less than 15 000 passenger units annually are not included in the data sets.

For more informaiton please refer to  https://www.cso.ie/en/methods/transport/aviationstatistics/ which is prepared for the data collection at national level. Some additional information are included in the Country Specific Notes (CSNs) available as an Annex to Eurostat’s metadata file. 

Airports are classified according to ICAO (International Civil Aviation Organization) airport coded as listed in ICAO document 7910.

Aircrafts are classified according to aggregated aircraft categories based on the ICAO aircraft codes as listed in ICAO document 8643.

Airlines are classified according to the ICAO airline codes as listed in the ICAO document 8585. When providing the data to Eurostat, the region where they are licensed is coded accordingly either as European Union (EU) or outside the European Union (non-EU).

Air transport - commercial air services for the airports with traffic in excess of 15,000 passenger units.

The five main Irish airports return data monthly. Dublin, Cork, Shannon, Kerry and Knock.

The regional airports return annual data only - Donegal, Inishmore and Connemara

The main concepts used in this domain are the following:

Community airport - a defined area on land or water in a Member State subject to the provisions of the treaty, which is intended to be used either wholly or in part for the arrival, departure and surface movement of aircraft and open for commercial air services.

Flight stage - the operation of an aircraft from take-off to its next landing. This is linked to the definition of passengers (or freight and mail) on board.

Passengers on board - all passengers on board of the aircraft upon landing at the reporting airport or at taking off from the reporting airport. All revenue and non-revenue passengers on board an aircraft during a flight stage. Includes direct transit passengers (counted at arrivals and departures).

Direct transit passengers - passengers who, after a short stop, continue their journey on the same aircraft on a flight having the same flight number as the flight on which they arrive.

Transfer of indirect transit passengers - passengers arriving and departing on a different aircraft within 24 hours, or on the same aircraft bearing different flight numbers. They are counted twice: once upon arrival and once on departure.

Freight and mail on board - all freight and mail on board of the aircraft upon landing at the reporting airport or at taking off from the reporting airport. All freight and mail on board an aircraft during a flight stage. Includes direct transit freight and mail (counted at arrivals and departures). Includes express services and diplomatic bags. Excludes passenger baggage.

On flight origin and destination - traffic on a commercial air service identified by a unique flight number subdivided by airport pairs in accordance with point of embarkation and point of disembarkation on that flight. For passengers, freight or mail where the airport of embarkation is not known, the aircraft origin should be deemed to be the point of embarkation; similarly, if the airport of disembarkation is not known, the aircraft destination should be deemed to be the point of disembarkation. This is linked to the definition of passengers carried and freight and mail loaded or unloaded.

Passengers carried - all passengers on a specific flight (with one flight number) counted once only and not repeatedly on each individual stage of that flight. All revenue and non-revenue passengers whose journey begin or terminates at the reporting airport and transfer passengers joining or leaving the flight at the reporting airport. Excludes direct transit passengers.

Freight and mail loaded or unloaded - all freight and mail loaded onto or unloaded from an aircraft. Includes express services and diplomatic bags. Excludes passenger baggage. Excludes direct transit freight and mail.

Passenger unit - one passenger unit is equivalent to either one passenger or 100 kilograms of freight and mail.

The data are collected at individual airport level.

Four categories of Community airports are defined by the Regulation (EC) N°1358/2003:

• Category "0": Airports with less than 15 000 passenger units per year are considered as having only "occasional commercial traffic" without obligation to report.
• Category "1": Airports with between 15 000 and 150 000 passenger units per year shall transmit only aggregated airport data (Data set C).
• Category "2": Airports with more than 150 000 passenger units and less than 1 500 000 passenger units per year shall transmit flight stage data, on flight origin destination data as well as aggregated airport data (Data sets A, B and C).
• Category "3": Airports with at least 1 500 000 passenger units per year shall transmit flight stage data, on flight origin destination data as well as aggregated airport data (Data sets A, B and C).

List of reporting airports by country with categories as from 2003 onwards is available in Eurostat metadata file (Annex) avia_pa_esms.

Airports under category ‘0’ are not included in the statistics provided to Eurostat.

Airports located in the the Republic of Ireland.

Passengers carried data are available from 1993. Passengers on board data are available from 2003. Freight and mail on board data are vailable from 2003 while Freight and mail loaded and unloaded are available from 1993. Direct transit passenger data are available from 2000 for Cork airport. Transfer passenger data are available from 2012.

Not applicable.

The units used depend on the variables collected within each data set and are: number of passengers, kilogrammes (for freight and mail), aircraft movements and passenger seats available.

According to the legal act the weight of freight and mail is transmitted in tonnes with three decimal places.

Reference period is the calendar year 2022.

National level:

• https://www.irishstatutebook.ie/eli/2020/si/10/made/en/print
• http://www.irishstatutebook.ie/eli/1993/act/21/enacted/en/html

European level: until 2002, the data were provided to Eurostat on a voluntary basis; since 2002 data provision is based on an EP and Council framework legal act and on several implementing Commission Regulations:

• Regulation (EC) No 437/2003 of the European Parliament and of the Council of 27 February 2003 on statistical returns in respect of the carriage of passengers, freight and mail by air.
• Commission Regulation (EC) No 1358/2003 of 31/07/2003.
• Commission Regulation No 546/2005 of 8 April 2005.
• Commission Regulation No 158/2007 of 16 February 2007.

Not applicable.

National level:

The confidentiality of all information provided to the CSO by individual respondents is guaranteed by law under the 1993 Statistics Act  (information provided will be treated as strictly confidential in accordance with Section 33 of the Statistics Act 1993.

European level:

• Regulation (EC) No 223/2009 on European statistics (recital 24 and Article 20(4)) of 11 March 2009 (OJ L 87, p. 164), stipulates the need to establish common principles and guidelines ensuring the confidentiality of data used for the production of European statistics and the access to those confidential data with due account for technical developments and the requirements of users in a democratic society.

The data provided to Eurostat in the data sets A1, B1 and C1 contain no confidential information.

The procedures with regard to statistical confidentiality folllows the Handbook on Statistical Disclosure Control (2010) and the 1993 Statistics Act.

Only the airline information data is subject to confidentiality. Before providing the data to Eurostat, the region where they are licensed is coded accordingly either as European Union (EU) or outside the European Union (non-EU).

The data provided to Eurostat in the data sets A1, B1 and C1 contain no confidential information.

Data confidentiality problems: 

 No problem to date. This is because of the time difference in submitting the data to the CSO and to Eurostat.

Air transport statistics for quarters one, two and three are published three months after the reference period. Quarter four and annual publication is published four months after the reference period.

Release dates are publicly available in the release calender of the CSO Ireland.

Since release dates are planned sometimes far in advance, changes of dates might occur. Therefore, the release calendar is updated continually.

The release calendar is publicly available on the website of the CSO Ireland.

Data is available to all users fee of charge. The quarterly and annual publications are published on the CSO website: Aviation Statistics releases.

More detailed results are available on the CSO PxStat database: Aviation Statistics

At the release date, air transport statistics is available to all users at the same time.

Air transport statistics are published quarterly. Air transport statistics for quarters one, two and three are published three months after the reference period. Quarter four and annual publication is published four months after the reference period.

Aviation statistics are published quarterly and can be accessed on the CSO website.

https://www.cso.ie/en/statistics/transport/aviationstatistics/

Aviation statistics are published quarterly and can be accessed on the CSO website.

https://www.cso.ie/en/statistics/transport/aviationstatistics/

Aviation statistical data can be accessed on the CSO StatBank Database

View Aviation Statistics on PxStat

Not applicable to air transport statistics.

Aviation statistical data is also published annually as a chapter within the Transport Omnibus

A Standard-documentation with Meta information (Definitions, comments, methods, quality) on Air Transport Statistics is available at national level. Some additional information are included in the Country Specific Notes (CSNs) available as an Annex to Eurostat’s metadata file.

Standard documentation with Meta information (Definitions, comments, methods, quality) on Air Transport Statistics is available at national level - Aviation statistics methodology. 

The system follows as far as possible the European Statistics Code of practice and Quality Assurance Framework of the European Statistical System, more precisely Principle 4: Commitment to Quality: Quality policy is defined and made available to the public. An organisational structure and tools are in place to deal with quality management. There are procedures in place to plan, monitor and improve the quality of the statistical processes.

Procedures based on quality reporting are in place to internally monitor product quality. Results are analysed regularly and improving actions are undertaken, if needed (for example after obtaining annual summary results and mirror checks reports from Eurostat). There is a regular and thorough review of the key statistical outputs.
Moreover, in the framework of Statistics the CSO  has introduced standard quality reports (standard-documentation) to be produced and kept up-to-date for all statistics. The reports are based on the ESS definition of quality in statistics and follow the European standard quality report and provide users with information about the underlying concepts, definitions, methods used and the quality of the statistics (meta-information) in a standardised format.

Data quality can be assessed as high. There is a set of validation rules and quality checks put in place, which detect various types of issues. In case of any issues detected, the data providers are contacted to provide explanations or/and revise the data accordingly. Checks for the consistency over times are prepared and reviewed.
Annually, Eurostat provides a data quality report with a summary of the main findings affecting quality as well as showing the solution adopted and the materiality of the existing differences. Mirror checks and checks for the consistency over times are prepared as well.
We have excellent cooperation with the relevant airports. Timeliness and punctuality are very good. Revisions concern only a few flights.

The key users of air transport statistics collected are:

• Department of Transport
• Eurostat
• Universities and research institutions
• Users involved in the aviation industry (e.g. airports, Irish Aviation Authority (IAA))
• general public

Data on commercial aircraft movements, the routes, numbers of passengers, amount of transported freight and mail as well as seats available provides an impportant basis for decision-making of politics, society and economy in the context of the development and promotion of transport projects.
Users demand for data regarding true origin and destination of the passengers and freight can not be fullfilled as such information is not collected within the data collection. These information is also not available from the airports.

There was no user survey specially carried out on air transport statistics data so far but direct feedback from main users like the Department of Transport, universities etc. highlights a good level of satisfaction regarding data coverage and availability.

The collection of data on air transport statistics is carried out in accordance with the provisions of Regulation 437/2003

Possibility to identyfy the true first origin/ final destination of a passenger: The OFOD would be on the flight data, but the Airports do not capture the true origin/destination of a passenger if they are making a transfer at either end of the flight. The airports do not get such ticket information from the airlines. It should also be noted that some people buy 2 independent tickets and it would be very difficult to track such passengers (e.g. a passenger may be taking a Ryanair flight from Dublin to Stansted and then an Easyjet flight from Stansted to Morocco). The DAA surveys passengers to give them an idea about the number of passengers who do take connecting flights and where they go.

Overall accuracy of the air transport statistics data is good. The processing with checks carried out before transmitting data to Eurostat provides a high accuracy of the data. 
For Table B1 the on flight origin/destination information of passengers on flights is not known or provided by the airports. The airports do not have such data. It should also be noted that some people buy 2 independent tickets and it would be very difficult to track such passengers (e.g. a passenger may be taking a Ryanair flight from Dublin to Stansted and then an Easyjet flight from Stansted to Morocco).
The number of transfer passengers in table C1 refers to the number of transfer passengers arriving and departing on flights (passengers are counted twice).

Not applicable for air transport data collection.

By working closely with the relevant airports, the various checks and the legal obligation to cooperate and report the data, misclassifications, under- or over-coverage can be excluded. Moreover, the correctness of the data is of great importance for the airports.
The use of the classification lists provided by Eurostat prevents a misclassification of aircraft types or partner airports.

All the statistics required by the provisions of the Regulation 437/2003 are transmitted to Eurostat within 6 months of the reference month.

All the statistics required by the provisions of the Regulation 437/2003 are available 1 months before the deadline for the data provisions set up in the legal act.

There are no problems of comparability for air transport data collection with a very high data comparability across contries due to the common legal basis. Comparisions of the data regarding passengers and freight/mail declared by partner reporting airports (so-called mirror checks) by Eurostat allow further the detection of possible inconsistencies which can be corrected if possible.

As from 2004 the statistics on air transport are comparable over time, as they are collected following fully the provisions of the legal act - the Regulation 437/2003. Time series checks are regularly made to detect inconsistencies in the data.

Time series breaks occur in case of airport being closed temporarily or permanently or in case an airport does not exceed the threshold of 15 000 passenger unit per year (and may be excluded from air transport data provisions). The detailed information on eventual breaks in the time series is provided in the Country Specific Notes (CSNs) available at Eurostat’s metadata page (in Annex part).

The data transmitted to Eurostat before 2004 consisted only of aggregates on passenger transport.

Comparisons with other transport statistics are only partially and to a limited extent possible with regard to freight transport and passenger transport, since data are currently not available or are not collected at the same level of detail and also different methods and underlying objectives.

When comparing transported freight with foreign trade statistics it has to be kept in mind, that foreign trade statistics exchange goods and their value between individuals while aviation statistics show the performance of the transport mode air.

As from 2004 the 3 data sets (A1, B1 and C1) collected and provided to Eurostat are consistent. 

The response burden is put on the airports, but is reduced to a minimum – the data users provide the data automatically via a data interface or email. The data providers are only contacted if minor errors cannot be solved by the CSO.

Air transport statistics for quarters one, two and three are published three months after the reference period. Quarter four and annual publication is published four months after the reference period. Revision may be required if for example information was received later than publication date. Mainly, those revisions would only concern a small amount of data and generally do not change the overall results of the already published quarterly data. In the case of any changes after the annual results have been published, then the public is informed in the form of footnotes to the revised PxStat tables on the CSO website.

See 17.1.

Dataset A1 – Data Suppliers (Passengers on board/Freight and mail on board):

Details supplied directly by the main Irish airports to the CSO. (Dublin, Cork, Shannon, Knock and Kerry).

Aircraft Information in A1:

The original information source that we use is the ICAO aircraft codes as available from Eurostat. These codes are also made available to the airports.

Seats information information in A1:

The original information source that we use is the file from Eurostat which details aircraft type and seat availability summary tables. These codes are also made available to the airports. Where a return is made by an airline/airport where the passenger seats aboard figure is less than the maximum seat capacity we do not make any changes. However if the return shows that the passenger seats aboard is greater than the maximum and the number of passengers is less than the maximum we adjust the seat capacity to the maximum as detailed in the file from Eurostat.

Dataset B1 –Data Suppliers (Passengers carried/Freight and mail loaded/unloaded):

Details supplied directly by the main Irish airports to the CSO.  (Dublin, Cork, Shannon, Knock and Kerry).

Dataset C1 - Details supplied directly by all Irish airports to the CSO.  (Dublin, Cork, Shannon, Knock, Kerry, Connemara Donegal, and Inishmore). 

Information needed for the datasets A1 and B1 are collected on a monthly basis from the main Irish Airports: Cork, Dublin, Kerry, Knock and Shannon.

Information for the C1 dataset is collected from all airports annually (main Irish airports supply total passenger numbers, freight, flights etc. ) for each month for this table.

Regional (Donegal, Connemara, Inishmore) airports supply totals for the year to the CSO.

Implementation of the data collection and compilation process :

CSO: The level of aviation data collected prior to the Regulation was very limited so a new data collection and compilation process was required to be put in place.
Airports: The Regulation had required an extension of an existing process

The data for the purpose of the Regulation 437/2003 is collected monthly with a xls/dat-file from the airports. The transmission is possible via a SFTP interface or via e-mail.

Data validation procedure and description of consistency checks :

The CSO runs the following checks on the data files received from the airports:

Seating capacity – look to see if there are more passengers than seats available.

Zero Returns – look to see if a return has been made for a passenger flight with zero passengers or a freight flight with zero freight.

Origin/Destination – run a check to see if flights included where origin is equal to destination.

Any errors that are found with the validations checks are queried, if necessary, with the airports by phone or email.

Data codification practices :

The Regulation codes are used by all airports.

After various checks, the data received from the airports are compiled into monthly data following the structure of the data sets which are preset by regulation (EC) 1358/2003. Data is transmitted to Eurostat via eDAMIS using SDMX files.

Not applicable for air transport data collection.

Not applicable.