Cheapest Airlines in the US – Budget Carrier Rankings 2026 by AirAdvisor

Amy Lancelotte

By:  Amy Lancelotte

9 minutes read

Last Updated:  27 August 2026

Flights can be one of the more expensive components of any trip, so it’s useful to know the cheapest airlines in the US if you need to save money. It’s not surprising that most of the USA’s low-cost carriers rank higher on our list of the cheapest airlines.

We reviewed the passenger average revenue per seat mile (RASM), which takes into account more than the base fare price. It includes things like seat selection and onboard services to get the full picture.

TL;DR

• The cheapest US airline overall is Frontier (RASM 2024/2025 = $0.0942).
• The most expensive US airline is Delta (RASM 2024/2025 = $0.1751).
• We reviewed 9 US airlines to determine the average passenger revenue per seat mile in 2024 and 2025. Then, the final rank was determined by averaging the RASM for both years.
• Compared to our 2025 overall ranking, every single airline had a decrease in the revenue average per seat mile.
• For 2026, Spirit Airlines was excluded since, as of May 2026, they no longer operate. Hawaiian Airlines was ranked last, as we could not find data for 2025 RASM.

Now, let’s get to our AirAdvisor list of the cheapest US-based airlines to fly in 2026. To form our top 9 list, we averaged out the revenue per available seat mile for each carrier in 2024 and 2025 (combined).

Top 3 Cheapest Airlines in the US

#1 Frontier Airlines

For the second year in a row, Frontier, an ultra-low-cost carrier, is the cheapest US airline:

• Lowest average revenue per seat mile of the 9 airlines we reviewed – $0.0942.
• Frontier’s score is more than $0.03 cheaper per mile than the next-cheapest airline.
• To put this difference in perspective, imagine you’re taking a flight from Seattle to Miami. The total distance is about 1,950 miles, so you could save $58.50 or more by choosing Frontier.

#2 Allegiant Air

In the #2 spot, we have Allegiant Air, which, unsurprisingly, is another ultra-low-cost airline.

• Allegiant’s revenue average per seat mile is $0.1249 for 2024 and 2025 combined.
• Very similar in size and reach to Frontier, Allegiant only covers US routes, so if you need an international flight, you’ll need to look elsewhere.
• Compared to our 2025 overall ranking, Allegiant moved up 3 spots, although 2 of those spots were due to the elimination of the now-defunct Spirit Airlines and the unavailability of 2025 data for Hawaiian Airlines.

#3 JetBlue

The fact that JetBlue is a low-cost airline (not ultra) means its position in the top 3 makes sense.

• JetBlue’s revenue per seat mile averaged out to $0.1293, not too far off Allegiant.
• Even though the fares and other services are cost-effective, JetBlue is among the most comfortable US-based airlines, so passengers with low budgets don’t automatically have to sacrifice comfort.
• Since last year’s ranking, JetBlue has only climbed one spot even though the RASM in 2025 was $0.0022 less than in 2024.

If you’ve experienced an unreliable airline and your flight has been delayed by 3 hours or more, compensation may be an optionUse our free flight checker to see if you qualifyCheck Your Flight

How the Others Stack Up – Spots 4 Through 9

#4 Southwest Airlines

The fourth-place spot belongs to Southwest, and this airline is the last discount carrier on our list. So, we can confidently say that the USA’s lower-cost airlines live up to their names.

• Southwest Airlines has a 2024/2025 RASM of $0.1311.
• While this is marginally higher than Allegiant’s, Southwest is the world’s largest low-cost carrier, so the direct destinations available are plentiful compared to both Allegiant and Frontier.
• Southwest has shown the biggest RASM decrease from 2024 to 2025, which was $0.0196. To use the earlier flight from Seattle to Miami, that could mean saving almost $40 by booking now instead of in 2024.

#5 Alaska Airlines

Alaska Airlines offers domestic flights and flights from US cities to Canada, Mexico, Costa Rica, Guatemala, the Bahamas, and Belize.

• The 2024/2025 revenue average per seat mile is $0.1390.
• From 2024 to 2025, the RASM decreased from $0.1399 to $0.1381, a marginal improvement.
• Alaska Airlines offers flash sales throughout the year, so it’s worth checking their prices, especially if you want to avoid a no-frills budget airline like Allegiant or Frontier.

#6 United Airlines

Now we’re getting into America’s largest airlines, and of the major international carriers, United is the cheapest:

• The average 2024/2025 RASM for United Airlines is $0.1642.
• United’s average revenue per seat mile is a full $0.025 higher than Alaska Airlines – that’s a huge gap.
• United flies worldwide, so if you’re planning to fly long distances, this is a solid option that will balance price and comfort.

#7 American Airlines

When it comes to affordability, the only thing we can say about American Airlines is that it’s not the most expensive US carrier.

• RASM for 2024 and 2025 for American is $0.1676.
• In 2024, the AA revenue per seat mile was $0.1693, and in 2025 it decreased to $0.1658, a positive trend that we like to see.
• American Airlines is another of the US’s major carriers with an enviable selection of routes. If you need to get somewhere on a certain day at a certain time, you can usually do it.

#8 Delta Airlines

Delta Air Lines is the most expensive of our 9 airlines, so if you’re dealing with a low travel budget, this should be the last airline you check.

• The average revenue per seat mile is $0.1751, significantly higher than American.
• Check Delta’s current flight deals page to save as much money as possible.
• Delta was the most comfortable airline in our 2026 study, so that can at least partially explain the higher prices.

If you’re one of the unlucky ones and experience an interruption on a Delta flight (or a flight from any other airline), we can help. It’s often possible to claim compensation for delayed flights, flight cancellations, and instances of denied boarding.

#9 Hawaiian Airlines

Fair or not, Hawaiian Airlines lands in the last spot, but we can’t definitively say it’s the most expensive because we don’t have the necessary data. Hawaiian is now a subsidiary of Alaska Air Group, which may explain why separate data isn’t available, even though the airline operates its own branded flights.

• The RASM for 2025 was unavailable at the time of publishing.
• In 2024, the RASM was $0.1216, so if that remains close to true in 2025, too, then Hawaiian Airlines would actually be in second place as a surprisingly cheap non-discount carrier.
• On the plus side, Hawaiian Airlines was our most reliable carrier for 2026 overall.

According to our extensive research, budget airlines aren’t always the most reliableIf you’ve flown with any of the airlines on our list and encountered a delay, you might be eligible for compensation.
Check now!

Cheapest International Airline in the US

Determining the cheapest international airline is easy if you take “international” in the truest sense of the word. Of the airlines that fly to any country other than the US, the cheapest airline would be the same as our overall winner, Frontier Airlines. They fly to the Caribbean, Mexico, and Central America. But, in truth, their destinations are quite limited.

For anyone searching for the cheapest international airline that flies to destinations like Asia, Europe, South America, and Africa, the frontrunner is United Airlines. Some other airlines fly to one or two of these destinations, but United Airlines is the cheapest carrier that has multiple flights throughout North America and 5 other continents.

AirAdvisor US Airline Affordability Rating – Top Carriers Ranked

Comparison: 2024 vs. 2025

Since we have data for both 2024 and 2025, we thought it would be useful to see which airlines’ revenue per seat mile increased year on year. Hint: it’s none – they all decreased, which is great news for passengers.

Southwest showed the highest decrease in average revenue per seat mile from 2024 to 2025. This was also true in our 2025 overall ranking, so Southwest seems to really be working to keep all flight costs as low as possible.

Our Methodology

To determine the cheapest airlines in the US, our methodology was fairly simple. We looked at each airline’s publicly available balance sheet for 2024 and 2025. We used the passenger average revenue per seat mile (RASM) and took the combined average of both years to rank them. The lower the dollar amount, the higher the ranking.

Choosing the Cheapest Airline for Your Next Trip

Many things go into determining the ideal airline for your next business trip or vacation. If you’d like an overall view of these same 9 airlines and how they rate in 9 different categories, including cost, check out our post on the Top Airlines in the US.

Our AirAdvisor Cheapest Airlines Score should be used anytime you’re planning to book a flight. When cost is important to you, check with the highest-ranked airline that flies to your destination first and then expand out from there. Many factors can influence the cost of an individual flight, like when you book and when you fly, and airlines also offer sales and discounts when flights aren’t as full as they want. Keep this in mind, and use our rankings as a guide to start your search.

FAQ

Author:

Amy Lancelotte

Job/Position: Senior Writer & Content Creator

Amy Lancelotte is a Senior Content Writer and editorial contributor at AirAdvisor with more than seven years of experience producing research-driven articles for global 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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