The assignment of these codes is governed by IATA Resolution 763, and it is administered by IATA headquarters in Montreal. The codes are published biannually in the IATA Airline Coding Directory. The codes are unique at any given point in time, although defunct codes may be re-used after a suitable period of time has elapsed. Many countries, such as Canada, no longer use IATA codes in their official aeronautical publications.
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.