A codeshare agreement, also known simply as codeshare, is a business arrangement, common in the aviation industry, in which two or more airlines publish and market the same flight under their own airline designator and flight number as part of their published timetable or schedule. Typically, a flight is operated by one airline while seats are sold for the flight by all cooperating airlines using their own designator and flight number.

An airline alliance is an aviation industry arrangement between two or more airlines agreeing to cooperate on a substantial level. Alliances may provide marketing branding to facilitate travelers making inter-airline codeshare connections within countries. This branding may involve unified aircraft liveries of member aircraft.