You bought a ticket for a flight. You show up to the airport and find your flight number on the departures board. So far, everything is normal. But when you show up to the gate, the airline you thought you were flying is nowhere to be seen and it’s a different airline’s logo on the side of the plane.
You just experienced a "codeshare."
Per the U.S. Department of Transportation (DOT), codesharing is “a marketing arrangement in which an airline places its designator code on a flight operated by another airline, and sells tickets for that flight.”
While it may seem counterintuitive, codesharing can be beneficial for both airlines and passengers.
It allows airlines to offer flights to destinations they don’t actually serve. It also helps with customer loyalty. For passengers racking up miles in attempts to earn frequent flier status, code-sharing makes it possible to earn points on a route your airline doesn’t presently offer.
However, it can also be deeply confusing. Problems could arise when checking a bag or when in need of customer assistance at the airport. While you may have purchased the ticket from one airline, the airline that’s operating the flight will be the main point of contact on the day of travel. Do not go to the counter of the airline that sold you the flight.
In 2011, the DOT made it mandatory for airlines to clearly disclose when a flight was operating as a codeshare. When this happens, the words “operated by” and the other airline’s name will appear on all ticketing information.