"The assignment of these codes is governed by IATA Resolution 767, and it is administered by IATA headquarters in Montreal. The codes are published tri-annually in the IATA Airline Coding Directory. The codes are not unique: 323 of the possible 17,576 codes are used by more than one airport.

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IATA also provides codes for railway stations and for airport handling entities. A list of airports sorted by IATA code is available. 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."