A codeshare occurs when one airline markets a flight operated by another airline. This may mean that you buy a ticket from United Airlines to Munich with a stopover in Frankfurt. While the first leg of your flight is operated by United, the second leg is flown by Lufthansa.

When a Lufthansa flight is "operated by United," it indicates a codeshare agreement, a common partnership in the airline industry. In this scenario, Lufthansa markets and sells the ticket under its own flight number (e.g., LH 9000), but the actual physical journey is conducted using a United Airlines aircraft, United flight crew, and United’s onboard service standards. This is very common because both airlines are founding members of the Star Alliance. For the passenger, the most important thing to know is that you must check in with the operating carrier (United) at the airport, not Lufthansa. While you may have booked through Lufthansa's website, United’s baggage policies and seat selection rules will generally apply to that specific leg of the journey. These partnerships allow airlines to offer a much wider network of destinations without needing to fly their own planes to every city, providing travelers with more flexible connection options and a single ticket for complex international itineraries.