Codeshare Flights Explained: Who Operates Your Flight and Why It Matters

What it means when a ticket says 'operated by' another airline, which rules and fees apply, where you check in, and how to tell before you book.

By WarBird Flight editors · Updated September 14, 2026 · 2 min read

What a codeshare is

A codeshare is one flight sold under two or more airline names. A ticket that reads Delta 7001 operated by KLM is a KLM aircraft and crew with a Delta flight number on it. Partners in the big alliances and joint ventures do this on most international routes and on many domestic connections to smaller cities.

Whose rules apply

The split is the same on every alliance, and it explains most codeshare surprises.

Baggage allowance: the rules of the airline whose ticket you bought, with some exceptions on separately ticketed segments.
Check-in, seats, and upgrades: the operating airline's systems. You often cannot pick a seat on the marketing airline's site until the day of travel.
Delays and cancellations: the operating airline handles rebooking at the airport; the ticketing airline handles refunds.
Frequent-flyer miles: credited by the program you choose, at that program's rate for the partner.

How to tell

Every itinerary must show 'operated by' next to a codeshare segment; look for it before paying. Flight numbers in the 3000 to 9999 range on a US carrier are usually codeshares or regional partners.

Why it matters when booking by phone

Agents can see the operating carrier, the aircraft, and whether the fare allows seat selection before ticketing. Call (708) 866-8751 and ask "who operates each segment" if you have a preference for a carrier's aircraft, a lie-flat seat, or a particular baggage allowance.