Codeshare agreements refer to the travel industry practice whereby individual airlines place their own reservation codes on another airline's flights. This enables them to provide routing for passengers on a single ticket, even though the flights may be operated by more than one carrier.
Codeshare agreements became a widespread industry practice in the early 1990's, and were originally a means to connect passengers easily with needed segments of international travel.
Almost every major airline participates in various forms of codeshare agreements, including domestic and international routing. Some even extend to rail travel to increase the scope of this full-service approach.
These often complex agreements between various airlines are subject to price and routing restrictions, and are determined by the inner workings of the "marketing carrier" and the "operating carrier."
Codeshare agreements allow airline carriers to offer passengers a single ticket on routes that are not serviced by one airline alone. They are able to cover more territory without the additional costs of new equipment and added employees.
When purchasing a ticket from an aircraft carrier, be sure to note whether it is "operated by" an entirely different carrier. When arriving at the airport, you will need to check in with the airline who is actually operating your flight, rather than the one who sold it to you.
When changes are needed to your reservation, or cancellations occur, you will need to contact the airline who actually ticketed the itinerary for you.
