The 10 Biggest Airlines in the US in 2026

American Airlines is the biggest airline in the US. It boarded 223.5 million passengers in 2025 and ended the year with 1,580 aircraft, more than any other US carrier once the regional jets flying as American Eagle are counted.

It is not the biggest on every measure, which is why other rankings disagree. Delta Air Lines brings in the most revenue, and United Airlines has the most mainline jets and flies the most seat-miles.

This list ranks the 10 biggest US passenger airlines by passengers carried in 2025, as each airline reported them, with fleet size and revenue alongside. It is current as of September 2026, which means Spirit Airlines is gone and two mergers have reshaped the middle of the table.

The top of the market is remarkably concentrated. According to OAG schedule data, the four biggest airlines hold 76% of all seats scheduled in the US for summer 2026.

Rank	Airline	Passengers, 2025	Fleet, end of 2025	Revenue, 2025
1	American Airlines	223.5 million	1,580	$54.6 billion
2	Delta Air Lines	200+ million	1,314	$63.4 billion
3	United Airlines	181.1 million	1,490	$59.1 billion
4	Southwest Airlines	168.3 million	803	$28.1 billion
5	Alaska Airlines (with Hawaiian)	58.6 million	413	$14.2 billion
6	JetBlue Airways	39.3 million	288	$9.1 billion
7	Frontier Airlines	33.2 million	176	$3.7 billion
8	Allegiant Air (with Sun Country)	18.5 million (about 22 million combined)	123 (195 combined)	$2.6 billion
9	Breeze Airways	About 6 million	50+	Private
10	Avelo Airlines	Not published	Not published	Private

Biggest by which measure? Three airlines can claim first

Ask which US airline is the biggest and the honest answer is: by what? Here is who wins on each common measure, using full-year 2025 figures unless noted.

Measure	Biggest	Runner-up
Passengers boarded	American, 223.5 million	Delta, 200+ million
Total fleet, including regional	American, 1,580	United, 1,490
Mainline jets	United, 1,066	American, 1,013
Seat-miles flown (ASMs)	United, 330.3 billion	American, 299.4 billion
Revenue	Delta, $63.4 billion	United, $59.1 billion
Seats scheduled, summer 2026	American, 160.5 million	Delta, 140.4 million

So is Delta or United bigger? Delta carries more passengers and earns more revenue. United has more aircraft and more mainline jets, and it flies about 11% more seat-miles than Delta, a reflection of its long-haul international network.

1. American Airlines

American boarded 223.5 million passengers in 2025, the most of any US airline, though slightly down from 226.4 million in 2024. Its 1,580 aircraft split into 1,013 mainline jets and 567 regional aircraft flying as American Eagle.

It also has the biggest summer 2026 schedule, with 160.5 million seats according to OAG, about 20 million more than Delta. American describes itself as the world’s largest airline and celebrates its centennial in 2026, a claim our ranking of the largest airlines in the world sets against its global rivals.

Size has not turned into money the way it has at Delta. American’s 2025 revenue of $54.6 billion was a record, but it grew just 0.8% and was the lowest of the Big Three.

The network is the strategic asset, with eight hubs in the 10 largest US metropolitan areas and Dallas Fort Worth the biggest. Scale also cuts both ways: Winter Storm Fern in January 2026 cancelled more than 9,000 American flights, the largest weather disruption in the airline’s history.

2. Delta Air Lines

Delta served more than 200 million customers in 2025 and ended the year with 1,314 aircraft. That is 989 mainline jets plus 325 regional aircraft flown as Delta Connection by Endeavor Air, SkyWest and Republic.

It is the biggest US airline by revenue, at $63.4 billion in 2025. That is $8.8 billion more than American earned from roughly 10% fewer passengers.

The difference is what Delta sells. Its premium-cabin ticket revenue reached $22.1 billion in 2025, almost level with the $23.4 billion it earned from the main cabin, and premium grew 7% while main cabin fell 5%.

The operation backs up the pricing. Cirium named Delta the most on-time US airline for the fifth year in a row, which is a large part of why it tops our list of the best airlines to fly in the US.

At the end of 2025 Delta offered up to 5,500 peak-day flights to more than 300 destinations on six continents, with Atlanta at the center of its domestic network.

3. United Airlines

United carried a record 181.1 million passengers in 2025, up 4.3%, and its $59.1 billion in revenue was also the highest in its history.

By physical size it rivals American. United ended 2025 with 1,490 aircraft, and its 1,066 mainline jets are the most of any US airline, 53 more than American.

It also flies people the farthest. United flew 330.3 billion available seat miles in 2025 (one seat flown one mile), about 10% more than American, helped by an average of 303 widebody departures a day.

United is the one growing fastest at the top. It says it grew faster than any other US airline in 2025, OAG put its summer 2026 capacity up 9%, and it plans to take delivery of more than 100 narrowbodies and about 20 Boeing 787s in 2026.

Run the arithmetic and the top spot looks less secure than it seems. If United keeps growing 4.3% a year while American shrinks 1.3%, United would pass American on passengers around 2029.

4. Southwest Airlines

Southwest boarded 168.3 million passengers in 2025, down from 175.5 million, with a fleet of 803 aircraft and record revenue of $28.1 billion.

It is the odd one out in the Big Four. Southwest earns about half of American’s revenue, yet by seats it outranks United, with 133.4 million scheduled for summer 2026 against United’s 127.7 million.

The reason is trip length. Southwest’s 180 billion seat-miles are just over half of United’s, spread across a similar number of boardings, so each seat travels a shorter distance and earns less.

2025 was also the year Southwest stopped being different. It introduced bag fees and a basic economy fare, and assigned seating began with travel on January 27, 2026.

5. Alaska Airlines (with Hawaiian)

Alaska Air Group carried 58.6 million passengers in 2025 across Alaska, Hawaiian and its Horizon regional arm. It ended the year with an operating fleet of 413 aircraft and $14.2 billion in revenue.

That makes it fifth, but the drop below the Big Four is a cliff. Alaska carries about a third as many passengers as Southwest, and the Big Four combined schedule 13 times its seats this summer.

The Hawaiian deal has made it a different airline. The two received a single FAA operating certificate in the fourth quarter of 2025, OAG counts them as one airline from April 22, 2026, and Alaska now calls itself one of four global US airlines, with Seattle flights to London and Rome from spring 2026.

It is ordering like one, too. In January 2026 Alaska placed the largest order in its history, for 105 Boeing 737-10s and five 787s, and plans a fleet of 475 aircraft by 2030.

6. JetBlue Airways

JetBlue carried 39.3 million passengers in 2025 and ended the year with 288 Airbus aircraft: 129 A320s, 100 A321s and 59 A220s.

It is the one big name going backwards. JetBlue’s revenue fell 2.3% to $9.1 billion in 2025, a year in which each of the Big Four reported record revenue.

Its biggest move is a partnership rather than a merger. The Blue Sky collaboration with United, announced in 2025, lets members earn and redeem points across both airlines.

JetBlue also finished simplifying its fleet, retiring its Embraer E190s in the third quarter of 2025 and leaving an all-Airbus operation.

7. Frontier Airlines

Frontier carried 33.2 million passengers in 2025 on a fleet of 176 Airbus A320-family jets, 60 of them A321neos, and earned $3.7 billion.

Spirit’s collapse left Frontier as the biggest ultra-low-cost airline in the US by passengers. Its second quarter of 2026 brought record revenue of $1.3 billion, up 38% on the year, on higher fares and capacity shifted into former Spirit markets.

OAG’s summer 2026 schedule shows how lopsided that contest had become: Frontier had 22.1 million seats on sale, while Spirit had already shrunk to 10.7 million before it stopped flying.

8. Allegiant Air (with Sun Country)

Allegiant carried 18.5 million passengers in 2025 with 123 aircraft and $2.6 billion in revenue. On May 13, 2026, it completed its acquisition of Sun Country Airlines, which carried 4.2 million scheduled passengers of its own.

Together the two fly 195 aircraft to nearly 175 cities and carry about 22 million passengers a year. Both brands keep flying separately for now.

Sun Country also brings a cargo business. It had 20 freighters at the end of 2025, in an operation that flies for Amazon Prime Air.

9. Breeze Airways

Breeze carried roughly 6 million passengers in the 12 months to November 2025. It flies more than 50 Airbus A220s with firm orders for 90 more, and it posted its first full year of net profit in 2025, four years after its 2021 launch.

Its niche explains the growth: roughly 90% of Breeze’s routes have no nonstop competition, according to Airways Magazine. OAG shows it with 6.8 million seats this summer, 10th in the country before Spirit’s exit moved it up a place.

10. Avelo Airlines

Avelo flew its 10 millionth customer in August 2026, five years after launching on April 28, 2021. It describes itself as the first new US airline in almost 15 years, and as the first US carrier to buy and fly the Embraer E195-E2.

That averages out to about two million passengers a year, roughly a third of Breeze’s recent pace, across 37 destinations in 15 states. It rounds out the list because the two carriers that used to sit between it and Breeze, Sun Country and Hawaiian, now belong to bigger groups.

Who are the Big Three, Big Four and Big Five?

The Big Three are American, Delta and United, the network airlines with global hubs and long-haul fleets. Between them they boarded more than 600 million passengers in 2025.

All three were built by consolidation. Each went bankrupt after 9/11 and then absorbed rivals that were among the biggest airlines flying in 2001.

The Big Four adds Southwest. By OAG’s count those four airlines hold 562 million of the seats scheduled for summer 2026, or 76% of the US market.

The Big Five usually means those four plus Alaska. Alaska draws the line differently, describing itself as one of four global US airlines, a framing that puts it alongside the three network carriers rather than Southwest.

The airlines missing from this list, and why

Spirit Airlines was still the ninth-biggest US airline by seats in April 2026. On May 2, 2026, it began an immediate wind-down and cancelled all flights, after two bankruptcies since 2024 and a jet fuel price spike tied to the war in Iran.

What remains is being sold off through the courts, and we explain who owns Spirit Airlines now in a separate piece.

SkyWest Airlines carried more than 46 million passengers in 2025, more than JetBlue, and flies over 500 aircraft. It does not sell its own flights, though: it operates through partnerships with United, Delta, American and Alaska, so its passengers board under those airlines’ regional brands.

United accounted for 41% of SkyWest’s departures in the second quarter of 2026, Delta 31%, American 19% and Alaska 9%.

Hawaiian Airlines and Sun Country Airlines still fly under their own names, but they are counted inside Alaska and Allegiant here because that is who owns them.

FedEx is smaller than most people assume. Federal Express had 698 aircraft on May 31, 2025, fewer than Southwest’s 803, and 253 of those were small Cessna feeder turboprops.

Will the ranking change?

Not through a merger at the top, for now. Talk of a United and American tie-up faded within weeks in spring 2026: American said it was not engaged with or interested in any discussions, and President Trump said he did not like the idea.

The movement is more likely to come from growth. United is gaining on American every year, Alaska is building toward 475 aircraft, Frontier is taking Spirit’s old markets, and Allegiant is folding Sun Country into one airline.

FAQ

What is the biggest airline in the US?

American Airlines is the biggest airline in the US by passengers and total fleet. It boarded 223.5 million passengers in 2025 and ended the year with 1,580 aircraft, including 567 regional aircraft flying as American Eagle. It also has the most seats scheduled for summer 2026, at 160.5 million according to OAG.

Is Delta or United bigger?

It depends on the measure. Delta carried more passengers in 2025, more than 200 million against United’s 181.1 million, and earned more revenue, $63.4 billion against $59.1 billion. United has more aircraft, 1,490 against 1,314, flies more seat-miles, and out-earns Delta once Delta’s third-party oil refinery sales are removed.

Who are the big 3 US airlines?

The Big Three are American, Delta and United, the network airlines with global hubs and long-haul fleets. Together they boarded more than 600 million passengers in 2025. Adding Southwest makes the Big Four, which hold 76% of US seats scheduled for summer 2026 according to OAG.

What are the big 5 airlines in the US?

The Big Five usually means American, Delta, United, Southwest and Alaska Airlines. Alaska, which now includes Hawaiian Airlines, is a distant fifth with 58.6 million passengers in 2025, about a third of Southwest’s 168.3 million.

Which US airline has the largest fleet?

American Airlines has the largest total fleet, with 1,580 aircraft at the end of 2025 counting 567 regional aircraft. United has the most mainline jets, 1,066 against American’s 1,013, and a total fleet of 1,490.

Which US airline has the highest revenue?

Delta had the highest revenue of any US airline in 2025, at $63.4 billion. That figure includes sales of gasoline, diesel and other non-jet products from the oil refinery Delta owns. Without those third-party refinery sales, Delta’s adjusted revenue was $58.3 billion, just below United’s $59.1 billion.

Is Southwest bigger than United?

Only on scheduled seats. Southwest has 133.4 million seats on sale for summer 2026 against United’s 127.7 million, according to OAG. United boarded more passengers in 2025, 181.1 million against 168.3 million, has nearly twice as many aircraft and earned more than twice the revenue.

What happened to Spirit Airlines?

Spirit Airlines stopped flying on May 2, 2026, cancelling all flights and beginning an orderly wind-down. It had filed for bankruptcy twice since 2024, and rising jet fuel prices tied to the war in Iran added to the pressure. Frontier, which carried 33.2 million passengers in 2025, is now the biggest ultra-low-cost airline in the US.