Green AirlinesWhich US airline gets the most out of a gallon of fuel?
In 2025, Frontier Airlines flew 83.0 passenger-miles on every gallon of jet fuel. Sun Country Airlines managed 53.0. That is a gap of 57% between the 13 airlines ranked here.
Ranking for 2025
Higher is better. The amber line on a bar is the range of our estimate for airlines that sell seats on regional partners' flights, explained below the table.
| # | Airline | Passenger-miles per gallon | kg CO2 per passenger-mile | Seat-miles per gallon | Load factor | Seats per flight | Average trip (miles) |
|---|---|---|---|---|---|---|---|
| 1 | Frontier Airlines | 83.0 | 0.117 | 105.8 | 78% | 209 | 938 |
| 2 | Alaska Airlines * | 78.5 | 0.124 | 94.7 | 83% | 96 | 1,293 |
| 3 | Spirit Airlines | 76.5 | 0.127 | 97.6 | 78% | 193 | 978 |
| 4 | Hawaiian Airlines | 73.2 | 0.133 | 87.9 | 83% | 170 | 1,666 |
| 5 | Allegiant Air | 70.3 | 0.139 | 85.2 | 83% | 175 | 915 |
| 6 | American Airlines * | 68.6 | 0.142 | 82.0 | 84% | 123 | 1,118 |
| 7 | Delta Air Lines * | 66.6 | 0.146 | 79.5 | 84% | 127 | 1,219 |
| 8 | United Airlines * | 65.5 | 0.149 | 79.8 | 82% | 126 | 1,480 |
| 9 | JetBlue | 64.9 | 0.150 | 78.8 | 82% | 158 | 1,357 |
| 10 | Southwest Airlines | 64.3 | 0.152 | 83.0 | 77% | 161 | 821 |
| 11 | Avelo Airlines | 62.3 | 0.157 | 82.2 | 76% | 167 | 841 |
| 12 | Breeze Airways | 62.1 | 0.157 | 80.5 | 77% | 135 | 883 |
| 13 | Sun Country Airlines | 53.0 | 0.184 | 63.4 | 84% | 186 | 1,276 |
* Airlines with regional partners. United, Delta, American and Alaska sell seats on flights that SkyWest, Republic, Envoy and other regional airlines operate. Those regionals report almost no fuel of their own, because the airline that sells the seats reports it. So the fuel in the filings covers both, but the miles are split between two filers. We put each regional flight back with the airline whose hubs it serves. For regionals that fly for one airline, the method assigns them correctly. For regionals that fly for several, the split is an estimate, and the amber line shows how much the answer moves. Details are on the methodology page.
What separates the top from the bottom
Passenger-miles per gallon is seat-miles per gallon multiplied by load factor. The first is about the aircraft and how the airline flies it. The second is how full the seats are.
Frontier Airlines gets 105.8 seat-miles from each gallon and fills 78% of its seats. Sun Country Airlines gets 63.4 seat-miles per gallon and fills 84%. Load factor ranges from 76% to 84% across the table, while seat-miles per gallon ranges from 63.4 to 105.8. The seat-miles side varies more: the best airline on it is 67% ahead of the worst.
Passenger-miles per gallon puts both together, which is why it is the main figure on this site. Fuel burned for cargo in the hold is not separated out, so airlines with large widebody fleets carry some fuel that belongs to freight. The methodology page covers this.