Survey Report Background Notes

Survey Report Background Notes

Survey Report Background Notes

The notes found on this page cover those previously found in the Passenger Survey Reports. 

Role of SSC

One of SSC’s Purposes and Aims is to provide statistical data that enables airlines, airports and other users to respond to demand. The Departing Passenger Survey provides comprehensive information on the nature of the passenger market at UK airports. It supports a wide range of analysis from forecasting air transport activity through to informing government policy.

While the survey, naturally, has a UK focus, a number of airline operators make use of survey research to understand better global interline patterns, such as London hub and spoke activities.

The success or failure of an air passenger survey depends to a large extent on the help and co-operation of the people on the spot. This involves not only the expertise of the interviewer and the willingness of the passenger to be interviewed, but also the attitude of airport staff, airline staff, immigration officers, security officials and others towards the presence of interviewers within or near their own working areas. We would like to thank all concerned for their assistance in helping to ensure the smooth running of the survey projects.

Survey History

Since 1968 a series of surveys has been undertaken to obtain information about air travellers and the determinants of the travel market. These surveys have been designed to obtain information of a kind that could not be collected on a routine basis from the air transport industry. The surveys have included questions on journey purpose, final and intermediate surface origins/destinations, means of transport to and from airports, route flown, country of residence and income. This information is used in assessing the type of market served by airports and consequently for forecasting air transport demand and for planning airport facilities.

Cycles of surveys were undertaken at major UK airports in the periods 1970-1972, 1975-1978, 1982-1987 and 1990-1996. Over each cycle, this gave 95% coverage of the total terminal passengers in the UK.

Ongoing Research

Following the 1996 survey, which ran at five London airports; Birmingham, Manchester and four Scottish Airports, demand built up for more regular survey data. After a consultation process involving all interested parties, it was decided to run a survey each year at Gatwick, Heathrow and Manchester Airports so long as sufficient sponsorship was forthcoming. Joining these Continuous Survey airports in 2001 were Luton and Stansted.

In parallel with the Continuous Survey, the Authority embarked upon a Regional cycle, which began in 1999. Reports on each of the surveys from this cycle are also available on the CAA website.


In planning the surveys of air passengers, a principal concern is to derive maximum value from the information collected, but at the same time to minimize passenger inconvenience. Therefore, in order to cause as little disruption to passenger flow as possible, it is necessary to impose a constraint on questionnaire length and content. To cause minimum inconvenience, most passengers are interviewed whilst waiting to board their aircraft.

The Authority uses its own field-force, managed by a project team in London. Shifts in each month are carefully structured so that all scheduled routes and, in most cases, all flights within a route are regularly sampled.


Several interested parties are consulted over the content of the questionnaires,including Government departments, airport management groups and airline management groups. The questionnaires are similar to previous survey questionnaires in that the same basic questions appear but some new questions are sometimes included specifically for the co-sponsors of the survey. A copy of a questionnaire used can be accessed on this site.


Referring to the tabulation section of the reports allows the reader to verify many of the facts and figures quoted throughout this report. Where possible, reference has been made to the relevant tabulation.

Throughout the creation of these reports, care and attention has been paid to the underlying data to ensure that an accurate and representative picture of travel movements can be provided. Where obvious data errors have been identified, (for example, a passenger travelling by surface means from Cornwall to Inverness Airport to catch a scheduled flight to Bristol), a correction has been made. There were few such errors identified.

Where interviews have been undertaken, but the passenger has been unwilling or unable to provide answers to certain questions, the responses have still been included in the sample, but an “unspecified” code has been used.

Where clarification is required in determining what base population to use, a footnote has been added.

Shift Allocation

A typical week was split into 14 sub-categories made up by the day of the week and the period (morning/afternoon). Interviewing shifts were selected to ensure that, over a 12-month period, an equal number of shifts were, where possible, in each of the above subcategories.


At all airports only departing passengers are interviewed, previous surveys having shown that differences in characteristics of arriving and departing passengers were not significant.

All passengers are eligable, apart from children less than two years of age.

A constant monitor of sampled flights was maintained throughout the year to ensure that as far as possible all routes, and in most cases individual flights, were covered regularly throughout the survey.

It was assumed that those passengers who were candidates for an interview, but for one of a variety of reasons could not be interviewed, had the same characteristics as those who were successfully interviewed. The overall interviewing success rate for the 2014 survey was 86%.

We have a dedicated web page that describes the Sampling methodologies employed at the surveyed airports.

Weighting General

The sampling and weighting of the surveys was conducted on a route-by-route basis at each of the survey airports.

Weighting refers to the ‘growing’ of the survey samples to represent actual traffic levels. A single sample record will correspond to a single passenger interview. The weighting process is conducted on a monthly basis, with adjustments made initially within the reporting quarter. Survey data, with provisional weights is then issued to customers on a quarterly basis throughout the 12-month survey period. CAA reserves the right to recalculate provisional quarterly weights throughout the survey period, in some cases reassigned populations against newly validated samples.

Creating Weights

The Weighting page summarises how scheduled and charter records are weighted, initially on a monthly basis, before annual and quarterly adjustments are introduced.


Passengers' use of airport

Terminating passengers are passengers who arrive at or depart from an airport by surface modes of transport.

Transfer passengers are passengers who change aircraft at the airport and have no other reason for visiting the airport. They can be divided into international-to-international, international to domestic, domestic to international and domestic-to-domestic Transfer passengers. A Transfer passenger constitutes two passenger movements; one arrival and one departure. A passenger interlining from one international flight to another counts as two international passenger movements. A passenger interlining from a domestic flight to an international flight counts as one domestic movement and one international movement.

There are two distinct types of international-to-international Transfer passengers - airside transfer and landside transfer. Airside Transfer passengers do not pass through immigration, but landside passengers do pass through immigration.

Transit passengers are passengers who arrive and depart on the same flight. These passengers do not pass the interview point and normally remain on the aircraft.

Terminal passengers are passengers who join or leave a flight at an airport; they include all passengers with the exception of transit passengers.

The diagram below shows how the classifications are connected.


Where a journey has been broken for a reason other than transit, it is considered torestart or finish at that point. The following examples illustrate the definition.

“Passenger A leaves home in Swansea, travels to Reading, has lunch and then flies out from Heathrow Airport."

This passenger's origin would be Swansea as their reason for being in Reading was transit.

"Passenger B, from Watford, travels to Amersham, has a business engagement, then goes onto Gatwick Airport and flies to Paris.”

This passenger's origin is classified as Amersham as her journey has been broken for a reason other than transit. A transit stop is defined as the point at which a passenger chooses to break his or her journey to the airport, the main reason for doing so being to rest, e.g. using airport hotels prior to early morning flights, calling in on or staying with relatives etc.

For the purpose of analysing the origins and destinations within the United Kingdom of terminating passengers, regions, areas and zones have been defined in terms of boundaries of, respectively, economic planning regions, counties and district council areas. The area of residence of UK residents was also recorded using the same zonal system.

UK and foreign passengers

A passenger is classified as a UK resident if the UK is the country in which he or she has lived for most of the last twelve months. Those residents in a country outside the UK are classified as foreign residents.

Business and leisure passengers

Journey purpose is classified as business or leisure in the following way.


  • Business
  • Attending internal company business
  • Meetings with customers/others
  • Conference/Congress
  • Trade Fair/Exhibition
  • Armed Services
  • Airline Staff
  • Contract Home Leave
  • Overseas Employment - Less than 12 months
  • Overseas Employment - 12 months or more
  • Studies paid by employer - Formal academic course
  • Studies paid by employer - Other
  • Au Pair
  • Olympics


  • Holiday - Fare paid separately
  • Holiday - IT/Package-Hotel
  • Holiday - IT/Package-Self Catering
  • Holiday - IT/Package-Cruise
  • Visiting friends and relatives
  • Migration
  • Studies (private/grants) - Formal academic course
  • Studies (private/grants) - Other
  • Cultural/sports
  • Unaccompanied school children
  • Other
  • Olympics

A further breakdown for passengers on skiing holidays was also included.

Domestic and international passengers

A passenger is classified as domestic if his flight is between two points, both of which are in the UK (including the Channel Islands). Otherwise he is classified as international.

Modes of transport

Mode of transport refers to the mode of surface transport used to arrive at the airport, which for outward air passengers, with the exception at Inverness, represents the last three modes of transport at all sites apart from Inverness.

Socio-economic group

The occupation group job dictionary produced by the Market Research Society was used to grade passengers.

Main Business

The SIC classification is used to code this information.

Tabular Means

In three of the tables that can be found in this report, means have been calculated to represent mean trip length (days), mean income (GBP) & mean age (yrs).

The mean category limits used to create these tables were trip length (49 days) for trips over 4 weeks, income (GBP 300,000) for income greater than £230,000 and age (88 yrs) for passengers older than 85 years.


© Civil Aviation Authority 2015

While every care has been taken to ensure that all figures quoted in this publication are correct, the Authority accepts no liability for errors made and any consequential misuse or misinterpretation of the data.

Extracts may be copied from this publication but CAA must be acknowledged as the source.