Codeshare flight — two carriers, one booking, who liable?

A codeshare flight is a commercial arrangement where two (or more) airlines sell the same flight under different flight codes. One aircraft, one departure time, two or more flight numbers. For the passenger this is often invisible until a problem occurs.

The two roles:

• Marketing carrier — the one you bought the ticket from. Their name + flight code on your booking confirmation (e.g. KL1234).
• Operating carrier — the one actually flying the aircraft. Their flight code also appears on your boarding pass (e.g. "Operated by Delta Air Lines, flight DL456").

Practical examples:

• KLM/Air France/Delta — SkyTeam alliance. A ticket bought at KLM may be operated by Delta (transatlantic) or Air France.
• Lufthansa/United/Air Canada — Star Alliance. Similar codeshare practice.
• British Airways/American Airlines/Iberia/Finnair — Oneworld.
• Plus non-alliance codeshares: KLM with Garuda, KLM with Saudia, etc.

For EU 261 claim — only operating carrier liable. The Van der Lans ruling (ECJ C-257/14) holds that EU 261 compensation is borne exclusively by the operating carrier, regardless of where you bought the ticket. The flightright ruling (C-274/16) broadens this: at multiple codeshare levels, the actually operating carrier remains the sole liable party.

Practical tip. Check your boarding pass for "Operated by [name]". That's the carrier to address your EU 261 claim to. CC the marketing carrier — but address the operator formally. Our codeshare bounce letter does this by default.

What if I had two separate tickets? That is NOT codeshare. Two separate bookings (two PNRs) with no interlink: you are responsible for the connection and cannot claim under EU 261 if the first carrier was delayed.