An IATA (International Air Transportation Association) code usually refers to an airline’s IATA airline designator code. IATA airline designators, sometimes called IATA reservation codes, are three-character codes assigned by the International Air Transport Association (IATA) to all the world's airlines.
Airline designator codes follow specific formats such as two alpha-numeric characters which are followed by an optional alpha character. Flight designators consist of the airline designator, "xx(a)", and the numeric flight number, "n(n)(n)(n)", plus an optional, "operational suffix" which is one alpha character, "(a)". This gives a full flight designator in the following format: "xx(a)n(n)(n)(n)(a)".
Designators are used to identify airlines for commercial purposes, such as reservations, timetables, tickets, tariffs, air waybills and in airline interline telecommunications. The format of the IATA codes provides only a limited number of codes that can be utilized, and therefore the IATA has specified that they will soon switch their airline code designators to ICAO codes which have proven to be much more flexible.