Interline vs Codeshare: What Changes on the Ticket, the Flight Number and the Baggage

Two carriers, one journey — but the agreement behind them decides whether one ticket can be issued, who owns the flight number, and which baggage rules apply.

Why this confuses agents

A passenger flying CAI–IST–BKK may see two different airline codes on the same booking. Whether that journey can travel on one ticket, and what happens when the first flight is late, depends on the commercial agreement between the two carriers, not on the itinerary itself.

Interline

An interline agreement lets one carrier issue a ticket that includes another carrier's flight. Each airline operates and markets its own flight under its own code. IATA Multilateral Interline Traffic Agreements (MITA) provide the standard framework for accepting each other's documents.

• Ticket: one ticket can cover both carriers when an interline agreement exists.

• Flight number: each segment keeps the operating carrier's own code.

• Baggage: the Most Significant Carrier principle in IATA Resolution 302 determines whose baggage rules apply to the whole journey.

• Disruption: re-accommodation is possible but depends on the scope of the agreement.

Codeshare

In a codeshare, one airline (the marketing carrier) sells seats on a flight physically operated by another airline (the operating carrier). The passenger sees the marketing carrier's code and flight number, and the display shows the operating carrier as a separate line.

• Ticket: sold as the marketing carrier's flight.

• Flight number: marketing code, with an operated-by disclosure that regulators require to be shown at the time of sale.

• Baggage and service: usually follow the marketing carrier's published conditions, but check-through and lounge rules vary by agreement.

What to check before you sell

• Does an interline or codeshare agreement exist between the two carriers on that route?

• Is the connection time above the published minimum connecting time at the transfer airport?

• Which carrier's baggage allowance governs the journey?

• Is the passenger told, before payment, who actually operates the flight?

Key takeaways

• Interline is document acceptance between carriers; codeshare is one carrier selling another's seats under its own code.

• The flight number tells you the marketing carrier, not always who flies the aircraft.

• Baggage on a mixed journey follows Resolution 302 logic, not simply the first carrier.