The flight number you book isn't always the airline that flies you. Here's the difference between marketing and operating carriers, codeshares, and wet/dry leases — and how it all shows up in the schedule.
Book a flight marked “QF” and you might board an aircraft painted in another airline’s colours, flown by another airline’s crew. That isn’t a mistake — it’s how the modern network works. Understanding the difference between who sells a flight and who flies it is essential to reading a schedule correctly, because the two aren’t always the same airline.
Two roles hide behind every flight:
On a plain flight, they’re the same airline. On a codeshare, they differ.
A codeshare is a commercial agreement in which two or more airlines sell the same physical flight under their own flight numbers. It lets a carrier offer a destination it doesn’t fly itself — feeding traffic across a partnership or alliance — without putting an aircraft there. The operating carrier flies once; several marketing carriers may sell it, each under its own code.
In the SSIM schedule, the operating flight is a flight-leg record (type 3); the codeshare marketing designators travel as segment-level data (type 4 DEIs) attached to that leg. Read the leg and you know who flies; read the segment data and you know who else is selling it. Miss the segment data and a schedule looks complete but hides half the commercial picture.
Leasing is the other reason the airline on the aircraft may not be the one you expect. The distinction is about what comes with the aircraft:
| Lease | What’s included | Crew provided by | Typical term |
|---|---|---|---|
| Wet (ACMI) | Aircraft, Crew, Maintenance, Insurance | Lessor | ~1–24 months |
| Damp | Aircraft + cockpit crew (not cabin) | Mixed | Short-term |
| Dry | Aircraft only | Lessee (on its own AOC) | ~2 years+ |
Under a wet lease (ACMI), one airline supplies a fully crewed, maintained, insured aircraft to another and is paid by the hours operated — common for covering seasonal peaks, delivery gaps, or disruptions. Under a dry lease, only the airframe changes hands; the lessee puts it on its own operating certificate and flies it with its own crew. (A codeshare and a wet lease are not the same thing — one is about selling another airline’s flight; the other is about getting access to more aircraft.)
This isn’t trivia. Getting the operating-versus-marketing relationship right drives real outcomes:
The schedule doesn’t just say when a flight operates. It says who operates it and who’s allowed to sell it — and those are three different facts that have to line up.
Reading a schedule correctly means keeping the operating leg and its codeshare segment data together, distinguishing marketing from operating flights, and not conflating them when you count or compare. That’s exactly the kind of fidelity SSIM Toolkit is built for: parse the record types faithfully, keep the segment data attached to the right leg, and let you see — clearly and locally — who flies and who sells, without a home-grown script guessing at it.
Next: SSM and ASM — how changes to all of this travel between systems.
Sources
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