4 Biggest US Airlines - Largest Carriers in the United States

Amy Lancelotte

By:  Amy Lancelotte

10 minutes read

Last Updated:  July 17, 2026

Have you ever wondered about America’s biggest airlines? We have, so we put together a list based on the latest full-year (2025) data for annual passengers, daily flights, fleet size, and available destinations. Although the top 4 largest airlines in the US might be somewhat obvious, we’re getting to the bottom of just how big these carriers are. Further down, we also rank the next-biggest US carriers and cover the 2025-2026 shake-up that reshaped the list, including Spirit’s shutdown and the Alaska-Hawaiian merger.

Here’s a summary of what we found:

• American Airlines transports the highest number of passengers (by a long shot).
• American Airlines offers the most daily flights.
• American Airlines has the largest fleet.
• American Airlines serves the most destinations, with United a close second.

To make a long story short, American is the largest US airline by every metric, but the other 3 airlines are still worthy of mentioning. Let’s see how everything stacks up.

Overall Largest Airline in the US - American Airlines

After compiling the data, a clear winner emerged and that’s American Airlines. Of the 4 categories we reviewed, American didn’t fall short in a single one. They carried the most passengers in 2025 (over 223 million) and offered the most daily flights. 

Passenger volumes are probably the best indicator to determine the biggest US airlines, as that’s typically what people think of. In the case of American Airlines, they carried over 23 million more passengers than the next-biggest airline.

The American Airlines Group publishes daily flight numbers, and that includes the regional airline affiliate of American Eagle. Their total is around 6,800 daily flights, and even after we remove the American Eagle regional flights, American Airlines still offers roughly 5,200 mainline daily flights. 

The American Airlines fleet size is currently around 1,580 aircraft, including regional American Eagle jets. It takes a lot of planes to transport all those passengers! They also reach the most destinations, although as their name suggests, their routes have a US focus.

This mammoth is showing no signs of slowing down, either. They’re doing their best to hold on to the top spot in fleet size. American announced on March 4, 2024, that they are adding a further 260 aircraft to their fleet. According to their CEO, Robert Isom:

Over the past decade, we have invested heavily to modernize and simplify our fleet, which is the largest and youngest among U.S. network carriers.

The company’s CFO also stated that:

We are very pleased to continue our longstanding partnerships with Airbus, Boeing, and Embraer with these orders. As we look into the next decade, American will have a steady stream of new aircraft…

We’ll wait to see how the others respond!

• More than 223 million passengers annually.
• Around 6,800 daily flights.
• 1,580 total aircraft.
• 350+ destinations, many in the US.

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The Second-Largest US Airline - Delta

Although Delta takes second place for the largest airlines in the U.S., that doesn’t mean they’re in any way small. Although the airline has a fleet of around 1,290 aircraft, Delta transported the second-highest number of passengers in 2025, which was 200 million. On average, Delta Airlines operates up to 5,500 daily flights, second only to American.

To take more of an overall view, Delta was actually our top-rated US airline and scored high points for reliability, so the biggest isn’t always better. But, if you do have issues with punctuality with any US airlines, it’s good to know what kind of compensation you’re entitled to. If you don’t want to go it alone, we can help you claim your US passenger rights.

• 200 million annual passengers.
• Up to 5,500 daily flights.
• Around 1,290 aircraft.
• Over 300 worldwide destinations.

Third Place - United Airlines

When it comes to variety, United Airlines flies to more than 60 different countries. This is the most of any US-based carrier. As a result, United lands in third place overall, even though the airline carried over 181 million passengers in 2025, the third-highest in the top 4. That is now more than Southwest, and a big jump from previous years.

United Airlines operates around 4,500 daily flights and has a fleet of over 1,500 planes (about 1,525), the second-largest after American. As for the actual destinations, passengers can reach nearly 400 cities across six continents. If your United flight from Europe is delayed or cancelled, you may also be covered by EU 261 compensation.

• Over 181 million passengers in 2025.
• Around 4,500 daily flights.
• About 1,525 planes in total.
• 390+ destinations worldwide.

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Fourth-Biggest US Carrier - Southwest Airlines

Although Southwest takes the last spot in our top 4, the airline still deserves consideration when discussing America’s biggest airlines. To provide context, Southwest served over 168 million passengers in 2025. Its passenger count now sits fourth in the top 4 after United pulled ahead, and its smaller fleet, daily flights, and destination network keep it in fourth overall.

They have the smallest fleet with 803 planes and routes that reach 117 (mostly domestic) destinations. As for daily flights, Southwest operates more than 4,000 a day during peak travel.

• Over 168 million passengers per year.
• More than 4,000 flights daily.
• 803 aircraft.
• 117 destinations across the US, the Caribbean, and Central America.

Largest US Airlines Data Summary

*Based on the airlines’ 2025 fact sheets and annual reports and Wikipedia’s List of largest airlines in North America.
**Fleet figures include mainline and regional affiliate aircraft, per the airlines’ 2025 filings and FlightRadar24.

Point Values

To determine the overall points for each of the top 4 airlines, we used 4 categories: annual passengers, number of daily flights, total fleet size, and reachable destinations. The airlines were ranked from 1-4, with 4 being the best and 1 being the worst. The higher the number of total points, the better. And since we deemed the number of annual passengers as the most important criterion, we assigned this category a 2x multiplier.

Why the Biggest US Airline Depends on the Metric

Ask which US airline is the biggest and the honest answer is "it depends on how you measure it." Our ranking above leads with annual passengers, which puts American on top. Switch the metric and the order moves:

• Passengers carried: American Airlines leads with about 223.5 million in 2025.
• Available seat miles (capacity across distance): United is actually first, at roughly 330 billion ASMs in 2025, ahead of American and Delta (around 299 and 298 billion). United flies longer average routes, so it moves more capacity even while carrying fewer passengers.
• Revenue: Delta is the money leader, with full-year 2025 operating revenue of about $63 billion, ahead of American at roughly $54.7 billion.
• Daily flights and fleet: American wins both.

So there is no single "largest" carrier. American is the biggest by the metrics most travelers care about, but United and Delta each top the list on their own measure.

Beyond the Big Four: The Next-Largest US Airlines

The Big Four dominate, but they are not the whole story. Together, American, Delta, United, and Southwest control roughly three-quarters of US seat capacity, which leaves a competitive second tier fighting for the rest. Here is how the next-biggest US airlines ranked by passengers carried in 2025.

Alaska Airlines is comfortably the fifth-largest US carrier once you fold in Hawaiian, which it now operates under a single certificate. JetBlue holds sixth on the strength of its East Coast and transatlantic network, while Frontier and Spirit are the big ultra-low-cost names. Allegiant rounds out the group with its leisure-focused, point-to-point model.

*Spirit Airlines ceased all operations on May 2, 2026. Its 2025 passenger total is shown for context only.

The 2025 Shake-Up: Spirit Shuts Down and Alaska Absorbs Hawaiian

Two events reshaped the bottom half of this list, and any current ranking has to account for them.

Spirit Airlines Shut Down in May 2026

Spirit ceased all passenger flights on May 2, 2026, after 34 years in the sky. The carrier had filed for Chapter 11 bankruptcy twice in under a year, and its second reorganization collapsed when a sharp jet-fuel price spike and failed rescue financing drained its remaining liquidity. Spirit was still the eighth-biggest US airline by 2025 passengers, so its exit removed a major ultra-low-cost competitor from the market almost overnight. If you held a Spirit ticket, our guide to your US air passenger rights explains where you stand.

Alaska and Hawaiian Now Fly as One

Alaska Air Group completed its takeover of Hawaiian Airlines, and the FAA granted the combined company a single operating certificate on October 29, 2025. The two brands are moving onto one passenger system and the Alaska "AS" code, and together they carried roughly 58.6 million passengers in 2025. That merger is what pushes Alaska clearly into fifth place, ahead of JetBlue.

Now that we’ve covered the U.S. largest airlines, you know that American Airlines is by far the winner in terms of passengers, flights, and fleet. Will this information impact your future decisions when searching for air travel options? Larger airlines can mean the potential for more logistical problems, including flight cancellations, overbooking and denied boarding, and significant delays. Just make sure you choose wisely!

At AirAdvisor, we hold even the largest airlines in the US accountable. So, if you encounter a flight interruption while traveling on any of these airlines, let our airline compensation experts help you claim flight delay compensation, get a flight refund, or secure a flight cancellation payout. You don’t have to face these giants alone!

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FAQ: Biggest US Airlines

Author:

Amy Lancelotte

Job/Position: Senior Writer & Content Strategist

Amy Lancelotte is a Senior Content Writer and editorial contributor at AirAdvisor with over seven years of experience producing research-based articles for international audiences. Her work focuses on travel, aviation, and air passenger rights, with an emphasis on factual accuracy, verified data, and clear, reader-first explanations.

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