Airline loyalty programs have evolved significantly from a simple point of differentiation to a crucial source of profits in their own right. Nowhere is this more true than in the US, where credit cards are generally quite popular (a key part of how airlines earn money from loyalty programs) while the airlines themselves are also huge. American, Delta, and United are the three largest airlines in the world, and they also operate the three world’s largest loyalty programs in virtually every category.

As airlines have become increasingly skilled in monetizing their frequent flyer programs, they’ve invested heavily in making the program more appealing to potential new members as well. Through various features and benefits, the carriers are now better than ever at getting people to sign up, which means more people using miles, which means that program partners need to purchase more miles from the airline, increasing profits. These are, as of 2026, the world’s largest airline loyalty programs by membership.

IAG Avios

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IAG (International Airlines Group) is a holding company that owns British Airways, Iberia, Aer Lingus, Vueling, and LEVEL. Although the airlines operate separately with their own operating certificates, they all use IAG Avios as their loyalty currency. Each airline has its own loyalty program that is separate from Avios, but uses it as the program’s currency, while IAG itself runs Avios as a program for the carriers. Some non-IAG airlines also use Avios as a loyalty program currency, including Qatar Airways and Finnair.

IAG has over 70 million customers worldwide using Avios, which makes it the fifth-largest program in the world as well as the largest program not operated in the US. British Airways is a behemoth in the European airline industry in large part because London has virtually limitless demand, while Aer Lingus and Iberia are also strong carriers within their home markets. These numbers are also boosted by the fact that Avios is used by non-IAG airlines, with Qatar Airways being particularly influential in this regard.

Europe is a highly competitive market that also features two other major airline groups, in the form of Air France-KLM and Lufthansa Group. Air France-KLM is the smallest of the three, but Lufthansa Group is larger than even IAG in multiple metrics, standing as Europe’s second-largest airline group behind only the Ryanair Group. However, Avios remains the larger program compared to Lufthansa’s Miles and More, and has become a common currency within the larger oneworld ecosystem.

Southwest Rapid Rewards

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Southwest Airlines is one of the world’s largest airlines, and in the US, it’s only outshone by American, Delta, and United. However, while it has a similar number of mainline narrowbodies, those three airlines also operate widebodies. In addition, Southwest does not have a regional airline brand, whereas the legacy carriers’ regional brands each operate with hundreds of aircraft. While Southwest is a ferocious competitor, it is significantly smaller than the legacies when you look beyond mainline fleet sizes.

It’s believed that Rapid Rewards may have nearly 100 million registered members, easily making it the number-four program in the US. Much like the competition, Rapid Rewards is a revenue-based program where mileage earning and spending rates are determined by how much you spend within the airline’s ecosystem. However, the program is structured differently, as Southwest has two premium tiers followed by its ‘Companion Pass’, which is mainly its own product rather than being a distinct loyalty tier.

Southwest Airlines has traditionally been a unique carrier in terms of the passenger experience. The carrier operated with open seating and gave free checked bags, but practices like these ultimately left money on the table. In an effort to increase profits, the carrier has been revising its commercial strategy and policies to better match its practices with the legacy carriers. This includes getting rid of open seating, adding extra legroom seats, and charging for checked bags, while it’s developing a new premium credit card tied to a lounge system.

American AAdvantage

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American Airlines’ AAdvantage program is one of the oldest airline loyalty programs in the world, and while American itself is struggling compared to its direct rivals, AAdvantage is still a popular program. It’s estimated that AAdvantage has over 115 million members, which makes it the world’s third-largest frequent flyer program. While this is a massive number, the US airlines don’t regularly disclose what their frequent flyer membership numbers truly are, which means that this number is likely even higher.

American has its basic membership tier, as well as four elite tiers. In addition, there’s also the airline’s ‘ConciergeKey,’ which is an elusive invitation-only tier with even more benefits. The airline partners with Citi for its credit cards, of which there are four personal cards and one card for business owners. In addition, American formerly also partnered with Barclays for co-branded credit cards, but it discontinued this card earlier in 2026 to consolidate its credit card portfolio with Citi.

American has not been making money, likely in part because there simply isn’t a lot of excitement or interest in the brand. Loyalty programs thrive on engagement by getting customers to use their credit cards more often, sign up for even more credit cards, and encourage others to join the program. American has not been focusing on high-spending markets like the Northeast, while it has a smaller long-haul network and less premium cabin capacity than its competitors. AAdvantage is still tremendously successful, but these factors do diminish interest in the airline.

Delta SkyMiles

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Delta SkyMiles is the largest loyalty program in the world by valuation, and it’s exceptionally important to the carrier’s profits. Delta is the US’s most profitable airline, and this is entirely because of SkyMiles. It’s estimated that there are over 120 million SkyMiles members, and the program is unbelievably popular because Delta is an upscale brand that is desirable to customers. As such, consumers continue to sign up to join SkyMiles, and more people than ever are also signing up for a SkyMiles co-branded credit card.

Delta Air Lines partners with American Express for its co-branded credit cards, and this agreement is incredibly lucrative. The airline sells its miles at incredibly high rates to Amex, and the issuer keeps buying miles at a rapid pace because demand is so strong. Delta brings in over $8 billion in revenue from its Amex agreement, and this revenue comes with almost no cost, making it incredibly high-margin. What’s more, Delta has focused on increasing its credit card footprint in high-spending areas of the country.

Delta SkyMiles has its basic membership tier, along with four elite Medallion tiers. In addition, the carrier operates its own invitation-only status, titled ‘Delta 360’. The airline offers four co-branded Amex cards along with three business cards, with annual fees ranging from zero to $650. In addition, the airline has several partnerships with companies like Starbucks and Uber, while its membership in SkyTeam means that you get reciprocal alliance status. The same is true for American Airlines and oneworld.

United MileagePlus

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United Airlines has been closely following the Delta strategy of how to move upmarket and build a premium brand that is desirable to consumers. As such, MileagePlus has become more popular than ever, and United recently revealed that it has over 130 million MileagePlus members, which is the highest figure ever disclosed by any airline. Of course, it’s worth keeping in mind that airlines don’t disclose these numbers very often, and it’s possible that AAdvantage and SkyMiles actually have more members. Based on publicly available information, however, MileagePlus is number one.

MileagePlus has a basic membership tier, along with four elite ‘Premier’ status tiers. In addition, United also has an invitation-only tier, which is called ‘Global Services’. The carrier partners with Chase for MileagePlus co-branded credit cards, which include four personal cards and two cards for small business owners. United’s annual fees for its co-branded credit cards max out at $695, which ties with American’s top credit card for the highest annual fee of any co-branded credit card, while Delta’s top card has an annual fee of $650.

United MileagePlus is excelling for more or less the same reason that SkyMiles is, as there’s a tremendous amount of interest in the brand, which increases demand for miles. Because these miles have almost no cost, United is earning a huge amount of money from these transactions. This isn’t a zero-sum game; Delta continues to excel and is the country’s most profitable airline, but United is excelling in a way that it never has before in modern history, and the carrier is by far the US’s second-most profitable airline.