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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsAn interline agreement lets one airline sell a journey that includes flights or other services provided by another airline. For travelers, that can make a multi-airline trip available on one itinerary, but it does not automatically settle whether bags will be checked through or what happens if a flight is disrupted. Those details depend on the ticket, airlines, airport and applicable conditions.
What an interline agreement means
IATA defines interline as “one airline selling an itinerary to a customer that involves services provided by another airline.” In practice, the arrangement lets airlines combine parts of their networks so a customer can travel between places that one airline might not serve alone. IATA describes this as a way to extend the origin-to-destination markets airlines can offer and give passengers access to more itineraries.
Interline cooperation can cover more than the sale of a connecting flight. Depending on the arrangement, it may support reservations, ticketing, pricing, baggage handling, departure control, disruption procedures, and the billing and settlement between airlines. The scope is not identical for every pair of airlines or itinerary.
How interline differs from codeshares and alliances
Interline is a broad category of cooperation, not another name for a codeshare or an airline alliance. IATA lists interline arrangements alongside distinct commercial structures such as individual agreements, codeshares, joint ventures and alliances. An airline may cooperate with another airline in one way without every benefit applying to every trip they sell together.
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In particular, alliance membership by itself does not establish that a specific itinerary is ticketed as an interline journey or that bags will be checked through. Check the ticket and baggage arrangements for the actual flights rather than relying on the airlines’ branding or alliance affiliation.
What the arrangement means for a traveler
Buying a trip with more than one airline
Interline can allow one airline to sell transportation that another airline operates. A single booking reference is not, by itself, proof that every flight is issued on one ticket or that the same conditions apply to all segments. Ask the airline or seller whether the whole journey is issued on one ticket and identify the ticketing or validating carrier.
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Connecting checked bags
Bags may be transferred between flights, but do not assume they will be checked to the final destination in every case. IATA’s baggage guidance addresses journeys on one ticket that include connecting transportation on two or more flights. Avianca says bags are automatically transferred to the final destination in the case described in its consumer guidance, while also noting that security authorities may require passengers to collect them and advising travelers to check the allowance in their ticket details.
At check-in, ask where the bag is tagged and read the destination printed on the baggage tag. Also confirm whether you must reclaim and recheck it at the connecting airport. The airline combination, ticket, airport procedures and security or immigration requirements can affect the answer.
Delays and cancellations
IATA describes getting customers to their final destination during an operational disruption as part of the interline framework’s customer promise. That description is not a universal legal guarantee for every itinerary. The rebooking conditions for a particular trip depend on its ticket and applicable terms, so contact the ticketing airline or booking seller to find out who handles a delay or cancellation and what alternatives are available.
What MITA and BIETA are
The Multilateral Interline Traffic Agreement (MITA) is IATA’s standard agreement framework for airlines. IATA says it sets out the legal framework, responsibilities, liability provisions and general procedures for interline partnerships. Its MITA manual includes passenger and cargo agreements, as well as rules on collecting money and issuing documents for travel on other carriers’ services.
BIETA files complement MITA by listing bilateral electronic-ticketing agreements outside the MITA framework. These are airline-industry resources, not consumer travel products. Travelers generally need to verify their own ticket conditions rather than consult the professional agreement files.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to check an interline itinerary before travel
- Confirm ticketing: Ask the airline or seller whether all flights are issued on one ticket, and which airline is the ticketing or validating carrier.
- Confirm baggage handling: Ask whether the first airline will tag your checked bag to the final destination. Check the tag at the airport and verify the baggage allowance in your ticket details.
- Check the connection procedure: Ask whether you must collect and recheck your bag, and whether security or immigration procedures at the connecting airport require you to reclaim it.
- Know whom to contact if plans change: Ask the ticketing airline or seller which party handles rebooking if a flight is delayed or cancelled, and what conditions apply to your ticket.
The term “interline agreement” alone does not answer these itinerary-specific questions. The airline combination, ticket, airport and applicable conditions determine what happens.
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How widely interline is used
IATA’s white paper It’s time to rethink IATA interline reported that more than 8% of passenger segments flown by IATA member airlines had been sold by other airlines, based on IATA Direct Data Solutions data, and estimated more than USD 52 billion in annual interline revenue for the total airline industry, based on WATS 2018. These are historical 2018 estimates in a paper published around 2019, not current measurements.
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