Questions about travel on a code-share trip or code-share partners.
A codeshare (or code-share) is an arrangement through which one transportation company sells passage on another's service as if it were providing the service itself. The term derives from the assignment of different codes (e.g. flight numbers) to a common service.
This arrangement has become extremely commonplace in commercial aviation. For example, codesharing is standard with so-called regional or express airlines; a United Express flight operated by SkyWest will be known to almost all passengers only by its United Airlines flight number.
Usually when the term is used, it refers to the looser codeshare arrangements that are part of airline partnerships and among the large international airline-alliances. A single flight may have as many as a dozen different flight numbers from as many unfamiliar airlines.
Sample Airlines (IATA code: SA) operates Flight 100 from AAA to BBB. This flight is coded in booking systems as SA100. It has a partner, Illustration Air (IATA code: IA). Through their codeshare agreement, Illustration Air sells seats on SA100, but it codes them as IA Flight 1201, and those seats now appear in booking systems as IA1201.
In this scenario, the marketing carrier is Illustration Air for those who book the flight as IA1201, and Sample Airlines for those who book the flight as SA100. In both cases, the operating carrier is Sample Airlines— that is, the one whose aircraft and crew (in frequent flyer slang, the metal) actually operate the flight.
Codeshare flights were created to benefit airlines, to give the impression of additional routes or frequencies and to offer sales through additional channels. They can be confusing to passengers, however, and passengers should exercise care when booking such flights to understand the implications.
Check-in, seat assignments, meal preferences, baggage handling, and almost all other aspects of the flight are handled by the operating carrier. Staff at the marketing carrier may be completely unaware of the rules or procedures of the operating carrier. The only time the marketing carrier is relevant to most passengers is in the awarding of frequent flyer points, as some (but not all) partnerships assign different points depending on the code; and in some rebooking scenarios, as there may be rules specific to codeshares or to fare classes that codeshares can book.