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Rankings / Routes / Denver to Washington, DC

2025 flights

Denver to Washington, DC

Between Denver and Washington, DC, 2.5 million passengers flew nonstop in 2025, on 16 thousand flights of about 1,471 miles and 3.2 hours in the air. The average passenger accounted for about 192 kg of CO2 from the fuel burned, from 159 kg on Frontier Airlines to 202 kg on United Airlines.

  • 192 kgCO2 per passenger, average
  • 1,471 milesabout 3.2 hours in the air
  • 2.5 millionpassengers in 2025
  • 84%of seats filled

CO2 per passenger, airline by airline

CO2 per passenger by airline, Denver to Washington, DCBar chart of kilograms of CO2 per passenger on each airline between Denver and Washington, DC in 2025.050100150200Frontier Airlines159 kgSouthwest Airlines189 kgUnited Airlines202 kg
CO2 per passenger by airline, Denver to Washington, DCBar chart of kilograms of CO2 per passenger on each airline between Denver and Washington, DC in 2025.0100200Frontier Airlines159 kgSouthwest Airlines189 kgUnited Airlines202 kg
Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.
Denver to Washington, DC by airline, 2025
AirlineShare of passengersFlights (thousands)Main aircraftSeats per flightSeats filledkg CO2 per passenger
United Airlines55%8.0Boeing 737-900ER, Boeing 737 MAX 920485%202
Southwest Airlines31%5.6Boeing 737 MAX 8, Boeing 737-80017081%189
Frontier Airlines14%2.3Airbus A320neo, Airbus A320-20018885%159

What explains the differences

It's number 43 of the 100 busiest city pairs by passengers, and number 13 for the lowest CO2 per mile flown (0.13 kg per passenger-mile, number 1 being the lowest). A typical route of 1,471 miles in this set comes out at about 209 kg, so this one is 8.4% below it.

The flights use more than one pair of airports: DEN to IAD (48%), DEN to BWI (33%), DEN to DCA (18%). The figures here cover all of them.

The airlines on this route differ by 27% per passenger. Frontier Airlines burned 2,604 gallons per flight and 159 passengers on each, and United Airlines 3,591 gallons and 173 passengers. The gap comes from fuel burned per flight, a little of it offset by passengers per flight. Frontier Airlines flew 85% full here against 85% for United Airlines, flying mostly Airbus A320neo against Boeing 737-900ER.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 190 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 1.1% higher.

2019 compared with 2025

In 2019 the route carried 2.4 million passengers on 16 thousand flights. In 2025 it carried 2.5 million, up 6%, on 16 thousand flights, up 2%. The average flight had 173 seats then and 190 now, and 89% of them were filled against 84%.

CO2 per passenger was 192 kg in 2019 and 192 kg in 2025, unchanged. Fuel burned per flight was up 3.7% (3,018 gallons to 3,129) and passengers per flight were up 3.5% (154 to 159). The distance flown was about the same (1,471 miles then, 1,471 now).

United Airlines led in both years, with 46% of passengers in 2019 and 55% in 2025. Frontier Airlines lost the most, 18% to 14%. Spirit Airlines no longer reaches 1% of passengers, having had 3% in 2019.

Airline by airline, Frontier Airlines went from 169 kg to 159 kg per passenger (180 seats per flight to 188, main aircraft Airbus A320neo in both years); United Airlines went from 201 kg to 202 kg per passenger (180 seats per flight to 204, main aircraft Boeing 737-900ER in both years).

Denver to Washington, DC, 2019 and 2025
Measure20192025
Passengers (thousands)2,3912,525
Flights (thousands)15.615.9
Seats filled89%84%
Gallons of fuel per flight3,0183,129
kg CO2 per passenger192192
CO2 per passenger by airline, 2019 and 2025, Denver to Washington, DCBar chart of kilograms of CO2 per passenger on Denver to Washington, DC for each major airline in 2019 and in 2025.050100150200United Airlines 2019201 kgUnited Airlines 2025202 kgSouthwest Airlines 2019188 kgSouthwest Airlines 2025189 kgFrontier Airlines 2019169 kgFrontier Airlines 2025159 kg
CO2 per passenger by airline, 2019 and 2025, Denver to Washington, DCBar chart of kilograms of CO2 per passenger on Denver to Washington, DC for each major airline in 2019 and in 2025.0100200United Airlines 2019201 kgUnited Airlines 2025202 kgSouthwest Airlines 2019188 kgSouthwest Airlines 2025189 kgFrontier Airlines 2019169 kgFrontier Airlines 2025159 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.

Denver to Washington, DC and back: time in the air

Flights from Washington, DC to Denver spent 208 minutes in the air on average in 2025, against 172 minutes from Denver to Washington, DC: 36 minutes longer, 21% more. That's the westbound direction, into the prevailing west-to-east winds, which at flight levels often blow at well over 50 miles an hour.

At this route's average burn of about 988 gallons per flight hour, those extra minutes cost about 595 gallons per flight, which is about 3.7 gallons or 36 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
Washington, DC to Denver208.17,907
Denver to Washington, DC172.07,969

Fly or drive

Driving is about 1,721 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 511 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 166% more than the 192 kg for a passenger on the flight.

With 3 people in the car, driving comes out lower per person than the flight (170 kg each, and 128 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 678 kg per vehicle.

CO2 per person by way of travel, Denver to Washington, DCBar chart of kilograms of CO2 per person flying, driving or taking the train between Denver and Washington, DC.0200400Flight, average192 kgCar, driver alone511 kgCar, 2 people256 kgCar, 4 people128 kg
CO2 per person by way of travel, Denver to Washington, DCBar chart of kilograms of CO2 per person flying, driving or taking the train between Denver and Washington, DC.0200400Flight, average192 kgCar, driver alone511 kgCar, 2 people256 kgCar, 4 people128 kg
CO2 per person, Denver to Washington, DC. 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.

Routes with shared cities or nearby CO2 per mile

Los Angeles to Denver130 kg CO2 per passenger over 850 milesWashington, DC to Boston100 kg CO2 per passenger over 383 milesAtlanta to Washington, DC104 kg CO2 per passenger over 554 milesMiami to Washington, DC144 kg CO2 per passenger over 921 milesChicago to Las Vegas194 kg CO2 per passenger over 1,516 milesLos Angeles to Chicago225 kg CO2 per passenger over 1,739 milesAtlanta to Las Vegas229 kg CO2 per passenger over 1,747 milesChicago to Phoenix190 kg CO2 per passenger over 1,441 miles

Airports on this route: Denver International Airport, Washington Dulles International Airport, Baltimore/Washington International Thurgood Marshall Airport, Ronald Reagan Washington National 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.