<P> A seat can be purchased on each airline's designator and flight number, but is operated by only one of these cooperating airlines, commonly called the operating carrier or more precisely (and in line with definitions in IATA Standard Schedules Information Manual): "Administrating carrier". The term "code" refers to the identifier used in flight schedule, generally the two - character IATA airline designator code and flight number . Thus, XX123 (flight number 123 operated by the airline XX), might also be sold by airline YY as YY456 and by ZZ as ZZ9876 . Airlines YY and ZZ are in this case called "Marketing airlines" (sometimes abbreviated MKT CXR for "marketing carrier"). Most of the major airlines today have code sharing partnerships with other airlines, and code sharing is a key feature of the major airline alliances . Typically, code - sharing agreements are also a part of the commercial agreements between airlines in the same airline alliances . </P> <P> In 1967, Richard A. Henson joined with US Airways predecessor Allegheny Airlines in the nation's first codeshare relationship . The term "code sharing" or "codeshare" was coined in 1989 by Qantas and American Airlines, and in 1990 the two firms provided their first codeshare flights between an array of Australian cities and U.S. domestic cities . Code sharing has become widespread in the airline industry since that time, particularly in the wake of the formation of large airline "alliances ." These alliances have extensive codesharing and networked frequent flyer programs . </P> <P> Under a code sharing agreement, the airline that administrates the flight (the one holding the operational permissions, airport slots and planning / controlling the flight and responsible for the ground handling services) is commonly called the operating carrier, often abbreviated OPE CXR, even though the IATA SSIM term "Administrating carrier" is more precise . The reason for this is that a third carrier is involved, typically in the case that the airline originally planning to operate the flight needs to hire a subcontractor to operate the flight on their behalf (typically a wet lease, meaning an aircraft is leased with crew and all facilities to fly, commonly due to capacity limitations, technical problems etc .) In this case, the airline carrying the passenger should be designated the operating carrier, since it is the one carrying the passengers / cargo . </P> <P> When a flight is sold under several designators and flight numbers as described above, the one published by the "Administrating carrier" is commonly called a "prime flight" (as opposed to a codeshare marketing flight). </P>

Who is the operating carrier for a flight