If you’re planning a trip that involves flying with more than one airline, you might wonder how your baggage will be handled.
Will you have to collect your bags and check them in again at each stop? How much will you have to pay for baggage fees? What if your bags get lost or delayed?
These are some of the questions that travelers often have when they book flights with multiple airlines.
Fortunately, there is a solution that can make your travel experience smoother and easier: interline agreements.
In this post, we’ll explain what interline agreements are, how they affect your baggage, benefits and drawbacks, tips, and more!
Interline agreements are basic arrangements between airlines that make it easier for passengers to book and travel on multiple flights on different airlines.
Interline agreements allow passengers to check in only once for all the flights on the itinerary, receive all their boarding passes, and have their baggage transferred from the first airline to the second airline without having to collect it and drop it off again.
Interline agreements are different from codeshare agreements and joint ventures, which are deeper forms of partnership that involve sharing codes, revenue, scheduling and pricing on routes.
Interline agreements are especially useful for travelers when things go wrong, such as flight delays or cancellations, as they allow airlines to rebook passengers on other airlines without extra cost.
What Is an Interline Agreement?
An interline agreement is a basic partnership between two or more airlines that allows passengers to book connecting flights more easily.
Interline agreements simplify several aspects of your multi-airline itinerary, including:
Ticketing
Interline agreements allow airlines to sell tickets that include flights operated by other airlines.
For example, you can buy a ticket from American Airlines that includes a flight from New York to London on British Airways and a flight from London to Paris on Air France.
This way, you only need to make one booking and pay one fare for your entire journey.
Check-In
Interline agreements also allow airlines to check in passengers and issue boarding passes for flights operated by other airlines.
For example, using the same example as above, you can check in at the American Airlines counter in New York and receive boarding passes for all your flights.
This can save you time and the inconvenience of having to check-in at each connection of your trip.
Baggage Handling
Interline agreements also allow airlines to transfer baggage between flights operated by other airlines.
Using the same example as above, you can check your baggage at the American Airlines counter in New York and it will be automatically transferred to your connecting flights.
You don’t need to collect and re-check your baggage at each stop.
However, interline agreements are still subject to standard customs restrictions.
For example, in the US, passengers must collect their bags and clear customs at their first port of entry, regardless of whether they have an interline agreement or not.
Interline agreements are the most basic form of partnership you will find between airlines.
They do not involve sharing revenue, coordinating schedules, or aligning prices.
They simply make it easier for passengers to book and travel on connecting flights with different airlines.
How Is an Interline Agreement Different from Other Types of Airline Partnerships?
Interline agreements are not the only way that airlines can cooperate with each other. There are other types of partnerships that involve deeper levels of coordination and integration between airlines.
Here are some of the most common ones:
Codeshare Agreement
A codeshare agreement is a step up from an interline agreement. It allows airlines to place their codes (abbreviations) on each other’s flights and sell them as their own.
This means that travelers can book a flight with one airline but fly on another airline’s plane.
For example, Delta Air Lines flight DL1 from New York to London is also sold as VS4000 by Virgin Atlantic, KL6101 by KLM, and AF8991 by Air France as part of codeshare agreements or joint ventures.
When you book this flight, you can choose which airline’s code you want to use, depending on factors such as price, loyalty program, or seat preference.
A codeshare agreement can also make it easier for travelers to earn frequent flyer miles for the whole trip, as opposed to an interline agreement where miles are only eligible on the flights operated by the original airline.
Joint Venture
A joint venture is the most advanced form of partnership between airlines. It involves sharing revenue and costs on certain routes or markets, as well as coordinating scheduling, pricing, marketing, and service standards.
A joint venture is almost like a merger between airlines, except that they remain separate legal entities.
For example, Delta Air Lines has a joint venture with Air France-KLM and Virgin Atlantic on transatlantic routes.
This means that these airlines act as one big airline on these routes, offering more flight options, seamless connections, consistent service quality, and reciprocal benefits for frequent flyers.
A joint venture requires regulatory approval from the authorities of the countries involved, as it can affect competition and consumer rights.
How to Find Out Which Airline’s Baggage Allowances and Fees Apply to Your Trip
The easiest way to determine which airline’s baggage policy applies to your trip is to check your e-ticket or confirmation email.
Look for a section labeled “Baggage Information” or “Baggage Allowance” that displays the number of pieces or weight you can check in for each flight.
If your journey doesn’t include a checked baggage allowance, airlines must include the fees for purchasing a first and second checked bag.
You can also visit each airline’s website and enter your booking reference or ticket number to find more details about their baggage policies. Alternatively, you can contact their customer service or reservation center directly.
Now that you know how to find the baggage policy for your upcoming trip, let’s discuss how airlines decide which policy applies to multi-stop trips with interline agreements5.
How Do Airlines Determine Which Baggage Allowances and Fees to Apply?
The answer depends on several factors, such as:
The origin and destination of your journey
The First Marketing Carrier (FMC) of your itinerary (the airline whose code appears in the flight number of the first flight)
The Most Significant Carrier (MSC) of your itinerary (the airline that operates the longest or most significant flight of your itinerary)
The specific agreements between the airlines involved in the multi-flight itinerary.
There are different rules for different regions and scenarios, but here are some general guidelines:
Domestic U.S. and Canadian Itineraries
For domestic U.S. and Canadian itineraries, the First Marketing Carrier decides which baggage policy applies for the whole itinerary.
The First Marketing Carrier can choose to:
Apply its own baggage policy to the entire itinerary, or
Apply the Most Significant Carrier’s baggage policy for the entire itinerary.
If your domestic journey includes a stopover that is longer than 4 hours, you will be required to collect your checked bags from baggage claim at the connection and recheck them with your connecting airline.
You may have to pay baggage fees to recheck your bags.
International Itineraries that Begin or End in the U.S. or Canada
For U.S. international itineraries that begin or end within the U.S. or Canda, the First Marketing Carrier decides which baggage policy applies for the whole itinerary.
The First Marketing Carrier can choose to:
Apply its own baggage policy to the entire itinerary, or
Apply the Most Significant Carrier’s baggage policy for the entire itinerary.
If your domestic journey includes a stopover that is longer than 24 hours, you will be required to collect your checked bags from baggage claim at the connection and recheck them with your connecting airline.
You may have to pay baggage fees to recheck your bags.
International Itineraries that Travel Through the U.S. or Canada
For international journeys via the U.S. or Canada (where the journey begins and ends outside these countries), the Most Significant Carrier’s baggage policy applies for each flight in the itinerary.
Non- U.S. or Canadian International Itineraries
For international itineraries that doesn’t include the U.S. or Canada, the Most Significant Carrier’s baggage policy applies for each flight in the itinerary.
Although, the Most Significant Carrier is the standard most commonly used to determine an interline itinerary (80% of itineraries with interline agreements follow this convention), airlines aren’t bound to follow it.
Airlines are free to make their own agreements between each other, with specific rules and conditions. This applies to interline itineraries that don’t begin or end in the U.S. or Canada only.
The following table summarizes which carrier (airline) decides the baggage policy for a multi-flight itinerary with an interline agreement:
Itinerary with Interline Agreement
Determining Carrier
Domestic (within U.S. or Canada)
FMC
International to / from U.S. or Canada
FMC
International through U.S. or Canada
MSC
International (non- U.S. or Canada)
MSC
Which Carrier Determines Baggage Policies for Interline Itineraries
FMC = First Marketing Carrier
MSC = Most Significant Carrier
FMC / MSC and Carry On Baggage Allowances
It’s important to point out that the baggage rule (FMC or MSC) that is applied to your itinerary has a direct effect on your carry-on baggage allowances for each of your flights:
For flights where the FMC rule is applied, all airlines must abide by the FMC’s carry-on baggage allowance,
For flights where the MSC rule is applied, each airline applies its own carry-on baggage allowance.
Benefits of Interline Agreements
Interline agreements can make your travel easier, cheaper, and more convenient in several ways:
Here are some of the benefits of interline agreements:
You can book your entire itinerary with one airline or travel agent, instead of having to book separate tickets with different airlines.
You can save money by paying only one booking fee and one baggage fee for your entire itinerary, instead of paying multiple fees for each airline.
You can save time by checking in only once for all your flights and receiving all your boarding passes at once.
You don’t have to worry about collecting and re-checking your baggage at each airport, as your bags will be transferred automatically from one airline to another.
You have more flexibility in choosing your flights and connections, as you can combine flights from different airlines that may not have codeshare or joint venture agreements.
You have more protection in case of delays or cancellations, as the first airline will rebook you for free on another flight operated by any of the interline partners.
Drawbacks of Interline Agreements
Interline agreements have some drawbacks that you should be aware of before you book your flight.
Here are some of the disadvantages of interline agreements:
Although the baggage policy will be the same across your itinerary, you may experience different service standards for each airline, such as seat selection, meals, entertainment, etc., which can affect your comfort and satisfaction.
You may not be able to earn frequent flyer miles or enjoy other benefits (such as lounge access or priority boarding) for the entire itinerary, as each airline may have different rules and policies for their loyalty programs.
You may not have the best flight options in terms of duration or convenience, as interline agreements do not guarantee coordination or synchronization of flight schedules between airlines.
Interline itinerary fares can often be more expensive than purchasing separate tickets.
If an issue occurs during your journey, such as delayed bags at a connection, it can sometimes be difficult for an airline to take responsibility. You may find that each airline will refer you to the other airline to resolve the issue.
Interline Agreements and Low-Cost Airlines
Interline agreements are rare among low-cost airlines such as:
Allegiant Air
Southwest Airlines
Spirit Airlines
These airlines usually don’t support interlining at all, as they prefer to sell their tickets directly to consumers and avoid paying fees or sharing revenue with other airlines.
If you want to fly with these airlines, you will have to book separate tickets and handle your baggage and check-in yourself.
How to Find Out Your Airline’s Interline Agreements
Unfortunately, most airlines do not publicize their interline agreements with other airlines. They tend to focus more on promoting their codeshare agreements and alliances, as these are more lucrative than interline agreements.
However, an airline’s partners, whether through codeshare or alliance, imply that interline agreements exist between them.
The following tables include links to the airline partner pages for U.S., Canadian, and foreign airlines.
If you want to book a flight with an interline agreement, you have several options:
Online Travel Agencies
Online travel agencies (OTAs) such as Expedia, Orbitz, or Travelocity can display and sell interline itineraries from multiple airlines on their websites or apps.
You can typically identify interline or codeshare flights by the term “operated by.” If a multi-flight itinerary describes a segment as “self-transfer”, this is an itinerary that includes separate tickets. To take advantage of an interline agreement, these itineraries should be avoided.
They can also issue electronic tickets for interline flights and handle any changes or cancellations.
However, OTAs may not show all the possible interline options or the best prices as they depend on the data and inventory provided by the airlines or global distribution systems (GDSs).
OTAs can be a great tool to research a large number of itineraries at the same time, however I strongly recommend that you make your booking with your airline directly. You may find cheaper prices with OTAs, however their shortcomings become clear if something goes wrong during your journey.
Traditional Travel Agents
Traditional travel agents can also book interline flights for customers using their access to GDSs or direct contracts with airlines.
They can also provide personalized service and advice and handle any issues or problems that may arise.
However, travel agents may charge fees for their services and may not have access to all the interline agreements or fares that are available.
Airlines
Airlines can also sell interline flights directly to customers through their websites, call centers, or airport counters.
They can also issue electronic tickets for interline flights and handle any changes or cancellations.
However, airlines may not offer all the interline options or the best prices as they may favor their own flights or partner airlines over others.
Despite this, I would strongly recommend that you ALWAYS book your flights directly with the airline.
What to Do at Check-In
When you check in your baggage for an interline itinerary, you should:
Make sure you have your e-ticket or confirmation email with you, as well as your passport and visa (if required).
Tell the check-in agent that you have an interline itinerary and confirm which airline’s baggage policy applies to your luggage.
Ask the check-in agent to tag your baggage with the final destination airport code and give you the baggage claim tags.
Check that your baggage claim tags match your itinerary and keep them with you until you collect your baggage at the destination airport.
If you have a short connection or need to clear customs and immigration at the intermediate airport(s), ask the check-in agent if you need to re-check your baggage or if it will be transferred automatically to the next flight.
What to Do If Baggage Is Lost or Damaged on an Interline Itinerary
If you arrive at your final destination airport and your baggage is missing or damaged, you should report it immediately to the baggage service office of the airline that operated the last flight of your itinerary.
For example, if you fly from New York to London on American Airlines, and then from London to Paris on British Airways, you should report your baggage issue to British Airways at the Paris airport.
The airline that operated the last flight of your itinerary is responsible for handling your baggage claim and compensating you for any loss or damage, according to their own policies and the applicable laws and regulations.
However, they may also contact the other airlines involved in your itinerary to investigate the cause and location of the problem.
Therefore, it’s Important to provide as much information as possible about your baggage and your itinerary, such as:
Baggage tag numbers,
Flight numbers,
Dates and times of travel,
Description and value of your baggage contents.
Tips for Interline Agreement Itineraries
If you’re planning to book an interline itinerary, here are some tips to make your trip smoother:
Compare Prices and Options
You may find different fares and availability for the same interline itinerary depending on which airline you book with.
Compare prices and options from different airlines or online travel agencies before you book.
Check the Baggage Rules and Fees
Check which airline’s baggage rules and fees apply to your whole trip based on the MSC concept.
Make sure you comply with the weight and size limits and pay any applicable fees in advance to avoid surprises at the airport.
Check the Cancellation and Change Fees
Check which airline’s cancellation and change fees apply to your whole trip based on the FMC concept.
Be aware of the terms and conditions of your ticket and how much it will cost you to change or cancel your booking.
Confirm Your Flights and Seats
Confirm your flights and seats with each airline involved in your itinerary before you travel.
You may be able to select or change your seats online or by calling the airline.
You may also be able to check in online for some or all of your flights.
Allow Enough Time for Connections
Allow enough time for connections between different airlines, especially if you have to change terminals or go through security or customs again.
Hot Tip: If you’re connecting at an airport that you’ve never transited through before, check YouTube to see if there’s a walkthrough video of the airport available.
Chicago O’Hare Airport Walkthrough ORD Terminal 2-5
Keep Your Documents Handy
Keep your documents handy, such as your passport, visa, boarding passes, confirmation numbers, and contact details of each airline.
Although you’ve checked in for all your flights and have received your boarding passes, you may need to show them at different points of your journey.
Always Book Your Flights Directly with Your Airline
Booking directly with your airline offers you more flexibility and protection when things go wrong.
If you made your booking with a third-party travel agent, the airline may direct you to them to resolve your issue.
Avoid Purchasing Separate Tickets
Sometimes, it can be cheaper to purchase two separate tickets instead of buying them as one booking.
However, this saving does come with some drawbacks – the most significant being that your flights will probably not have an interline agreement between them.
Some airlines can still check your bags through to your final destination, depending on the airlines involved, but this is becoming increasingly rare. Often, it’s at the discretion of the airline agent at the check-in counter.
For example, British Airways doesn’t check through baggage on itineraries with separate tickets, even if both of the flights are operated by British Airways!
Final Thoughts
Interline agreements can make traveling on multiple airlines easier and less stressful for passengers, but they also require some research and planning ahead.
However, I think it’s well worth the effort. As someone who always checks a bag when traveling, not having to worry about collecting your luggage at each connection, is a welcome perk.
Remember to always check your airlines’ websites or contact their customer service for the latest information on baggage allowances and policies.
