Codeshare flights explained: why one flight has several flight numbers

You’re standing at the terminal looking at the departures board: for New York, there are three flights with the same time, the same gate and the same destination – only the flight numbers differ. Yet three aircraft won’t take off. What you’re seeing is a codeshare flight: a single flight that several airlines sell under their own numbers. This guide explains who flies and who only sells, why airlines do it, what rights you have as a passenger – and why only one airline counts at the fence, on the radio and on the flight tracker.

Codeshare: the short answer

A codeshare is an agreement between airlines to sell the same flight under several airline codes. One company operates the flight – it’s called the operating carrier. The others are marketing carriers: they include the flight in their timetable with their own flight number and sell seats on it, but use neither aircraft nor crew.

For the marketing airline, it’s a way to offer destinations it doesn’t serve itself. For the operating airline, it means additional sales channels and often fuller cabins. And for you as a passenger, it means: through tickets with connecting itineraries, baggage to the final destination and miles in your usual frequent flyer program.

Where the term comes from

The basic idea comes from US regional aviation. In 1967, Allegheny Airlines, a predecessor of US Airways, entered a partnership with the small Hagerstown Commuter of Richard A. Henson. The feeder flew short routes that weren’t worthwhile for the big airline, but the connections were marketed under the big company’s name. That is considered the first codeshare-like partnership in the US.

The term itself was coined by Qantas and American Airlines in 1989. In 1990, the first jointly marketed flights of the two companies between Australia and the US followed. With the rise of the big alliances in the 1990s, codesharing became a standard tool of the industry. Today, practically all major network airlines have codeshare partners, and many of them are organized in Star Alliance, oneworld or SkyTeam. How the three alliances are structured is explained in the overview Star Alliance, oneworld and SkyTeam.

Who flies, who sells? The roles in detail

In a codeshare, there is a clear division of labor. Knowing it helps you with travel planning just as much as with spotting.

Aspect	Operating airline (operating carrier)	Marketing airline (marketing carrier)
Aircraft and registration	provides them itself	no aircraft of its own on the route
Crew in the cockpit and cabin	own crew	none
Flight number	own “main” flight number	additional own number with its own IATA code
Callsign on the radio	yes, exclusively its own	doesn’t appear on the radio
Ticket sales	yes	yes, through its own channels
Liability under EU passenger rights	yes	no, claims go to the operator

What matters here: the partners’ additional flight numbers are purely commercial. They exist in the booking system, on your ticket and on the departures board. In air traffic control’s flight plan, on the other hand, only the operating airline’s flight appears.

What codeshare flight numbers look like

Each marketing airline assigns a flight number with its own two-character IATA code – how these codes work is explained in the article IATA and ICAO codes explained. Many carriers use high, four-digit number ranges for codeshares so that partner flights are easy to tell apart from self-operated connections in their own system. A Lufthansa flight to North America can thus additionally carry a number from United Airlines or Air Canada. That isn’t a fixed rule, though – each airline organizes its numbers itself, and assignments change with every timetable change.

What types of codeshare agreements are there?

How exactly the partners split the seats among themselves is governed by the respective contract. A few basic models have become established in the industry:

• Block space: The marketing airline buys a fixed allotment of seats at an agreed price and resells it at its own risk. If it doesn’t sell everything, the allotment is still paid for.
• Free flow (free sale): The partners’ booking systems are connected, and each airline may sell as long as the flight has seats. Settlement is based on tickets actually sold.
• Limited free flow: Like free flow, but each partner has an upper limit on seats.

In addition, a distinction is made as to which direction the agreement runs. In a reciprocal codeshare, both airlines put their code on each other’s flights. In a one-way codeshare, only one side markets the partner’s flights, for example when a big airline adds the routes of a small feeder to its network.

More than codeshare: joint ventures

On especially important markets, airlines go even further. In a joint venture, partners coordinate not only their flight numbers but also timetable, fares and, in part, revenues. Well known are the big transatlantic alliances in which, for example, the Lufthansa Group, Air France-KLM and Delta Air Lines take part. Such partnerships need antitrust clearance and go well beyond a simple codeshare. You’ll find details in the article Transatlantic joint ventures.

Why airlines enter codeshares

At first glance, it seems odd that competitors sell each other’s flights. For everyone involved, though, it pays off for several reasons.

The last point is no detail. Because each partner airline lists the flight in its own timetable, a route often appears several times on booking portals. If you don’t pay attention to “operated by,” you may end up comparing three offers that all end up in the same aircraft.

What this means for you as a passenger

In the EU, two sets of rules matter for codeshares. Regulation (EC) No. 2111/2005 of December 14, 2005 regulates not only the EU air safety list but also informing passengers about the identity of the operating air carrier. The basic idea: whoever sells a ticket must tell you which airline actually operates the flight – and inform you if that changes.

For delays, cancellations and denied boarding, the EU passenger rights regulation applies. Under these rules, the operating air carrier is liable, meaning the airline that operates the flight. If you bought your ticket from a codeshare partner, you therefore usually direct claims for compensation to the operator. For rebookings and refunds of the ticket price, on the other hand, the airline you booked with is often the contact.

In practical terms, that means for your booking:

• Look for “operated by.” This tells you the airline, the aircraft and usually the service standards on board.
• Check baggage rules. With codeshares involving different partners, free baggage and carry-on rules can differ.
• Clarify terminal and check-in. You often check in with the operator, and at some airports it sits in a different terminal than the airline on your ticket.

Codeshare, wet lease, regional partner: the difference

Codeshares are often confused with other forms of cooperation. For spotters, the distinction matters because it determines which livery and which registration you end up seeing.

Model	Who flies?	Flight number	Livery at the fence	Callsign
Codeshare	operating airline with its own aircraft	several, one per partner	the operator’s	operator
Wet lease	lessor with aircraft and crew	the lessee’s	often the lessor’s	lessee or lessor, depending on the agreement
Regional partner with branded appearance	regional airline on behalf of the big airline	the big airline’s	often the big airline’s brand	usually the regional airline’s
Air-rail	rail company	the airline’s flight number	a train	none – it’s a train

In a wet lease, an airline hires an aircraft with crew and sells the flight as its own. The article Wet lease explained covers that in detail. The regional partner model is especially common in North America: companies such as SkyWest Airlines fly for big network airlines under their brand and flight number. The aircraft wear the livery of United Express, Delta Connection or American Eagle, but the radio callsign is often the regional airline’s own. If you look for a United number on the live map, you may therefore find the flight under a completely different callsign.

What you really see as a spotter

For practice at the fence, the most important rule is simple: everything you can see, hear and track belongs to the operating airline.

• On the aircraft: Livery, registration and aircraft type are the operator’s. A partner airline that only sells tickets doesn’t appear on the aircraft – unless it’s one of the alliance special liveries presented in the article Alliance liveries.
• On the radio: Air traffic control knows only one callsign per flight. Why it sometimes doesn’t sound like a flight number at all is explained in the guide Callsign vs. flight number.
• On the flight tracker: Trackers show the callsign from the transponder. Some services additionally display codeshare numbers, but the position always belongs to the one real flight. Which apps work how is compared in the article Flight tracker apps compared.
• On the departures board: All flight numbers appear here. Several entries with the same time, the same destination and the same gate are almost always a single codeshare flight. How to use boards for planning is covered in the post Using departures and arrivals boards for spotting.

If you’re interested in a specific aircraft and not just the flight, the registration is the most reliable way. How to track an aircraft by registration or hex code is shown in the guide Tracking an aircraft by registration.

Watching codeshares at the hub

At big connecting airports, you see codeshares especially clearly. At Frankfurt Airport, many Lufthansa long-haul flights additionally carry numbers from Star Alliance partners, and conversely, German airlines sell seats on their partners’ flights. From the Zeppelinheim viewing platform, you can compare a look at the board in the terminal or in an airport app directly with what actually lands: three or four entries become a single aircraft.

It gets exciting when a partner operates its own flight. Then you see the foreign airline’s livery at the German airport, even though the flight is also sold in Germany under a Lufthansa number. The same applies in the other alliances, for example on flights of Air France and KLM that carry Delta numbers.

Codeshare with trains

Air-rail offerings are a special case. Here, a train connection carries a flight number so that train and flight can be booked on one ticket. In Germany, Lufthansa has for years sold selected ICE connections of Deutsche Bahn to the long-distance station at Frankfurt Airport with its own flight number. You won’t see any of this at the fence – but a flight number on the departures board can have a train behind it.

Typical pitfalls

• The flight number on the ticket is not the airline in the aircraft. What matters is always the “operated by.”
• Several flight numbers don’t mean several flights. On the board, count time, destination and gate, not the numbers.
• Codeshare is not wet lease. In a codeshare, the operator flies its own flight; in a wet lease, a lessor flies on behalf of another airline.
• Partner numbers are not permanent. Codeshare agreements are terminated, expanded or renegotiated. What applies in one timetable period can look different in the next.
• Search by callsign instead of by number. If you can’t find a flight on the live map under the partner number, search for the number or callsign of the operating airline.

Conclusion

At its core, a codeshare is a sales agreement: one airline flies, several sell. That explains the many flight numbers on the departures board, the “operated by” notes when booking and the fact that on the radio and the flight tracker there is still only one flight. For passengers, what matters most is which airline operates the flight – it’s liable in disruptions and determines service and baggage rules. For spotters, it’s even simpler: livery, registration and callsign always belong to the operator, and that’s exactly what you enter in your collection.