The interline, also known as interline and interline ticketing, is a voluntary commercial agreement between different airlines to treat passengers travelling on routes requiring several flights with several airlines. [1] Such agreements allow passengers to switch from one flight with one airline to another airline flight without having to pick up their baggage or re-register it. Airlines can also promise a free booking change if the service is interrupted due to a delay. Airlines participating in airline alliances such as Star Alliance, SkyTeam or oneworld almost always have interline agreements. But direct competitors can also benefit from Interline agreements. Most Interline agreements include a section on registration, which means that the customer only has to register once for the entire itinerary. This is usually the case for the airline that operates the first segment of the flight. However, if you are unsure, contact the airline to make sure you check in for the entire itinerary and with the right airline to avoid extra charges or missed flights. If two airlines have an interline agreement, they usually take care of check-in and baggage for passengers on the other side. This means that travellers must check in only once for all flights on the itinerary and that their luggage will be delivered from the first airline to the second, without having to pick them up and hand them over manually. Interline agreements differ from code-sharing agreements in that codeshare agreements generally relate to the numbering of a flight with the company`s code (acronym), although the flight is operated by another airline. However, codeshare relationships may affect whether an interline ticket (or e-ticket) can be issued, since the codeshare marketing carrier and code-sharing operator must have interline agreements with all other airlines in the itinerary for a single ticket to be issued.

Baggage for Interline flights usually means that airlines carry their luggage and ensure that it is transported to your final destination. This means that you will drop off your luggage at the departure airport and the airline will process it to your destination where you can pick it up. Some airlines do not participate in Interline agreements, such as Wow Air, which require passengers to process connections with other airlines as if they were the first flight of your trip, and the passenger must pick up their luggage and check it in with the next airline.