What does the airline term “codeshare” mean?

A codeshare is a flight marketed by multiple airlines under separate flight numbers.

In a codeshare agreement, one airline usually operates the aircraft and is called the operating carrier. One or more partner airlines sell seats on that same physical service using their own flight numbers. This lets airlines offer destinations beyond their own route networks.

For example, a passenger may buy a ticket from one airline while the ticket identifies another airline as the operator. Booking displays normally identify the operating carrier, and airport screens provide the actual flight information.

Codesharing is different from a merger or an airline alliance. An alliance is a broader cooperation structure, while a codeshare is a specific marketing and operating arrangement. It is also different from an interline agreement, which mainly concerns ticketing and baggage connections. Codeshares became especially common as airlines expanded network partnerships and coordinated connecting itineraries.