IATA airport code
An
IATA airport code, also known an
IATA location identifier or simply a
location identifier [
1], is a three-letter code designating many
airports around the world, defined by the
International Air Transport Association (IATA). They are published tri-annually in the
IATA Airline Coding Directory. The assignment of these codes is governed by IATA Resolution 767, and it is administered by IATA headquarters in
Montreal. IATA also provides codes for
railway stations and for airport handling entities. A
list of airports sorted by IATA code is available.
The codes are not unique: 323 of the possible 17,576 codes are used by more than one airport. The characters prominently displayed on baggage tags attached at airport check-in desks are an example of a way these codes are used.
While the IATA codes are the most familiar airport codes to passengers, the 4-letter
ICAO airport codes are becoming increasingly common within aviation. All international flights are flight-planned and tracked using ICAO (
International Civil Aviation Organization) designators, and most
GPS databases use
ICAO codes to avoid conflicts with three-letter navigation-aid codes. Many countries, such as
Canada, no longer use IATA codes in their official aeronautical publications.
A
list of railway stations codeshared in agreements between airlines and rail lines such as
Amtrak,
SNCF French Rail,
Deutsche Bahn,
Thalys International, and
Swiss Rail is available. There is also a separate
List of Amtrak station codes, three-character codes used by
Amtrak for its
railway stations in the
United States and
Canada.
*
Airport ABCs: An Explanation of Airport Identifier Codes*
Airport code database, search by name, country, code, etc.*
List of airport codes and locations, provided by Brussels Airport*
IATA Document Distribution*
Airliners.Net (airline codes in the forums can be identified by mouseover) 
