The International Air Transport Association and the International Civil Aviation Organization each issue codes for airlines, such as the IATA's AA for American Airlines and WN for Southwest Airlines and the ICAO's AAL for American Airlines and SWA for Southwest Airlines. Other IATA codes include DL for Delta Air Lines, KN for China United Airlines and FB for Bulgaria Air. Other ICAO codes include DAL for Delta Air Lines, CUA for China United Airlines and LZB for Bulgaria Air.
IATA codes are used to identify an airline, its destinations and travel documents, while ICAO codes are used as designators for airlines and other aircraft operating agencies, aeronautical authorities, airports and services. The IATA and the ICAO typically refer to codes for airlines as "airline codes" and codes for airports and destinations as "airport codes." IATA airline codes consist of two alphanumeric characters, while IATA airport codes consist of three letters. All IACO codes are composed of three capital letters.
IATA and IACO codes are unique at a given point in time; however, defunct codes may be re-used after a certain period of time. IATA.org features a tool for finding IATA codes, while AirlineUpdate.com features charts listing ICAO and IATA codes side-by-side.