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Rankings / Routes / Los Angeles to Seattle

2025 flights

Los Angeles to Seattle

Between Los Angeles and Seattle, 3.7 million passengers flew nonstop in 2025, on 31 thousand flights of about 959 miles and 2.2 hours in the air. The average passenger accounted for about 151 kg of CO2 from the fuel burned, from 108 kg on Frontier Airlines to 239 kg on SkyWest Airlines.

Alaska carries 63% of the passengers between Los Angeles and Seattle, the same share as in 2019, so the route's 151 kg per passenger is mostly Alaska's number: 138 kg, down from 149 kg in 2019. Delta went the other way, from 154 kg to 165 kg.

The regional flights are the weak spot. SkyWest carries 7% of passengers now, up from 2%, on 71-seat jets at 239 kg, 73% above Alaska's mainline jets and more than twice Frontier's 108 kg.

  • 151 kgCO2 per passenger, average
  • 959 milesabout 2.2 hours in the air
  • 3.7 millionpassengers in 2025
  • 81%of seats filled

CO2 per passenger, airline by airline

CO2 per passenger by airline, Los Angeles to SeattleBar chart of kilograms of CO2 per passenger on each airline between Los Angeles and Seattle in 2025.0100200Frontier Airlines108 kgAlaska Airlines138 kgDelta Air Lines165 kgUnited Airlines167 kgSkyWest Airlines239 kg
CO2 per passenger by airline, Los Angeles to SeattleBar chart of kilograms of CO2 per passenger on each airline between Los Angeles and Seattle in 2025.0100200Frontier Airlines108 kgAlaska Airlines138 kgDelta Air Lines165 kgUnited Airlines167 kgSkyWest Airlines239 kg
Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.
Los Angeles to Seattle by airline, 2025
AirlineShare of passengersFlights (thousands)Main aircraftSeats per flightSeats filledkg CO2 per passenger
Alaska Airlines63%17.2Boeing 737-800, Boeing 737-900ER16882%138
Delta Air Lines20%6.4Boeing 737-80015277%165
SkyWest Airlines7%4.7Embraer 1757182%239
Frontier Airlines4%1.0Airbus A320neo, Airbus A321neo19685%108
United Airlines4%1.2Airbus A320-200, Boeing 737 MAX 816373%167

What explains the differences

It's number 14 of the 100 busiest city pairs by passengers, and number 55 for the lowest CO2 per mile flown (0.16 kg per passenger-mile, number 1 being the lowest). A typical route of 959 miles in this set comes out at about 146 kg, so this one is close to that.

The flights use more than one pair of airports: SEA to LAX (49%), SEA to SNA (24%), SEA to ONT (16%). The figures here cover all of them.

The airlines on this route differ by 120% per passenger. Frontier Airlines burned 1,840 gallons per flight and 166 passengers on each, and SkyWest Airlines 1,424 gallons and 58 passengers. The gap comes from how many passengers share each flight, not from fuel burned per flight. Frontier Airlines flew 85% full here against 82% for SkyWest Airlines, flying mostly Airbus A320neo against Embraer 175.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 124 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 22% higher.

2019 compared with 2025

In 2019 the route carried 4.2 million passengers on 36 thousand flights. In 2025 it carried 3.7 million, down 11%, on 31 thousand flights, down 14%. The average flight had 141 seats then and 150 now, and 83% of them were filled against 81%.

CO2 per passenger was 161 kg in 2019 and 151 kg in 2025, down 6.6%. Fuel burned per flight was down 3.2% (1,937 gallons to 1,874) and passengers per flight were up 3.6% (117 to 121). The distance flown was about the same (959 miles then, 959 now).

Alaska Airlines led in both years, with 63% of passengers in 2019 and 63% in 2025. SkyWest Airlines gained the most share, 2% to 7%. Frontier Airlines and United Airlines didn't have 1% of the passengers in 2019 and now together carry 8%. Compass Airlines and JetBlue and Horizon Air no longer reach 1% of passengers, having had 15% in 2019.

Airline by airline, Alaska Airlines went from 149 kg to 138 kg per passenger (161 seats per flight to 168, main aircraft Boeing 737-800 in both years); Delta Air Lines went from 154 kg to 165 kg per passenger (168 seats per flight to 152, main aircraft Boeing 737-900ER then and Boeing 737-800 now).

The airports changed too: SEA to LAX handled 59% of the passengers in 2019 and 49% in 2025.

Los Angeles to Seattle, 2019 and 2025
Measure20192025
Passengers (thousands)4,2153,746
Flights (thousands)36.030.9
Seats filled83%81%
Gallons of fuel per flight1,9371,874
kg CO2 per passenger161151
CO2 per passenger by airline, 2019 and 2025, Los Angeles to SeattleBar chart of kilograms of CO2 per passenger on Los Angeles to Seattle for each major airline in 2019 and in 2025.0100200Alaska Airlines 2019149 kgAlaska Airlines 2025138 kgDelta Air Lines 2019154 kgDelta Air Lines 2025165 kgSkyWest Airlines 2019232 kgSkyWest Airlines 2025239 kg
CO2 per passenger by airline, 2019 and 2025, Los Angeles to SeattleBar chart of kilograms of CO2 per passenger on Los Angeles to Seattle for each major airline in 2019 and in 2025.0100200Alaska Airlines 2019149 kgAlaska Airlines 2025138 kgDelta Air Lines 2019154 kgDelta Air Lines 2025165 kgSkyWest Airlines 2019232 kgSkyWest Airlines 2025239 kg
Kilograms of CO2 per passenger on the airlines that flew the route in both years. 2019 figures use that year's filings and estimated aircraft fuel rates, with type-average replacements for missing or outlying filings as described in the methodology. Less is better.

Los Angeles to Seattle and back: time in the air

Flights from Los Angeles to Seattle spent 137 minutes in the air on average in 2025, against 131 minutes from Seattle to Los Angeles: 7 minutes longer, 5% more. The route runs mostly north to south, so the winds on the day, routing and congestion decide the difference.

At this route's average burn of about 840 gallons per flight hour, those extra minutes cost about 97 gallons per flight, which is about 0.8 gallons or 8 kg of CO2 for each passenger on the slower direction. The route figure above averages both directions.

Time in the air by direction, 2025
DirectionAverage minutes in the airFlights
Los Angeles to Seattle137.415,419
Seattle to Los Angeles130.515,460

Fly or drive

Driving is about 1,122 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 333 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 121% more than the 151 kg for a passenger on the flight.

With 3 people in the car, driving comes out lower per person than the flight (111 kg each, and 83 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 442 kg per vehicle.

CO2 per person by way of travel, Los Angeles to SeattleBar chart of kilograms of CO2 per person flying, driving or taking the train between Los Angeles and Seattle.0100200300Flight, average151 kgCar, driver alone333 kgCar, 2 people167 kgCar, 4 people83 kg
CO2 per person by way of travel, Los Angeles to SeattleBar chart of kilograms of CO2 per person flying, driving or taking the train between Los Angeles and Seattle.0100200300Flight, average151 kgCar, driver alone333 kgCar, 2 people167 kgCar, 4 people83 kg
CO2 per person, Los Angeles to Seattle. Driving figures divide one car's emissions between the people in it. See flying vs driving for other trip lengths.

Flights are listed under the airline that operates them, so regional flying appears under the regional. How the CO2 and drive figures are worked out is in the methodology.

What to take from it

The whole route is 7% cleaner per passenger than in 2019, 151 kg against 161 kg, while carrying 11% fewer people.

Half of the 'Los Angeles' passengers, 52%, don't use LAX, and with 1,122 road miles to Seattle a car of three would produce 111 kg each, 26% below the flight. The flight itself is about 134 minutes in the air.

Routes with shared cities or nearby CO2 per mile

Los Angeles to San Francisco75 kg CO2 per passenger over 337 milesLos Angeles to Las Vegas53 kg CO2 per passenger over 227 milesNew York to Los Angeles406 kg CO2 per passenger over 2,465 milesLos Angeles to Dallas-Fort Worth171 kg CO2 per passenger over 1,222 milesDenver to Phoenix93 kg CO2 per passenger over 602 milesMiami to Washington, DC144 kg CO2 per passenger over 921 milesChicago to Dallas-Fort Worth126 kg CO2 per passenger over 800 milesWashington, DC to Houston193 kg CO2 per passenger over 1,216 miles

Airports on this route: Seattle-Tacoma International Airport, Los Angeles International Airport, John Wayne Airport, Ontario International Airport, Hollywood Burbank Airport.

Airport and airline references

Source: US Bureau of Transportation Statistics (BTS), T-100 traffic and Schedule T-2 fuel filings; US EPA transport emission factors. See the methodology.

See all routes, or how the airlines compare overall on the airline pages.