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Rankings / Routes / Denver to Houston

2025 flights

Denver to Houston

Between Denver and Houston, 2.2 million passengers flew nonstop in 2025, on 14 thousand flights of about 869 miles and 2.0 hours in the air. The average passenger accounted for about 119 kg of CO2 from the fuel burned, from 98 kg on Frontier Airlines to 127 kg on Southwest Airlines.

  • 119 kgCO2 per passenger, average
  • 869 milesabout 2.0 hours in the air
  • 2.2 millionpassengers in 2025
  • 84%of seats filled

CO2 per passenger, airline by airline

CO2 per passenger by airline, Denver to HoustonBar chart of kilograms of CO2 per passenger on each airline between Denver and Houston in 2025.050100Frontier Airlines98 kgUnited Airlines119 kgSouthwest Airlines127 kg
CO2 per passenger by airline, Denver to HoustonBar chart of kilograms of CO2 per passenger on each airline between Denver and Houston in 2025.050100Frontier Airlines98 kgUnited Airlines119 kgSouthwest Airlines127 kg
Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.
Denver to Houston by airline, 2025
AirlineShare of passengersFlights (thousands)Main aircraftSeats per flightSeats filledkg CO2 per passenger
United Airlines61%7.6Airbus A321neo, Boeing 737-900ER20887%119
Southwest Airlines27%4.6Boeing 737 MAX 8, Boeing 737-70016580%127
Frontier Airlines12%1.5Airbus A320neo, Airbus A321neo20983%98

What explains the differences

It's number 56 of the 100 busiest city pairs by passengers, and number 23 for the lowest CO2 per mile flown (0.14 kg per passenger-mile, number 1 being the lowest). A typical route of 869 miles in this set comes out at about 135 kg, so this one is 12% below it.

The flights use more than one pair of airports: DEN to IAH (73%), DEN to HOU (28%). The figures here cover all of them.

The airlines on this route differ by 30% per passenger. Frontier Airlines burned 1,738 gallons per flight and 174 passengers on each, and Southwest Airlines 1,718 gallons and 132 passengers. The gap comes from how many passengers share each flight, not from fuel burned per flight. Frontier Airlines flew 83% full here against 80% for Southwest Airlines, flying mostly Airbus A320neo against Boeing 737 MAX 8.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 112 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 5.9% higher.

2019 compared with 2025

In 2019 the route carried 2.2 million passengers on 14 thousand flights. In 2025 it carried 2.2 million, up 4%, on 14 thousand flights, down 0%. The average flight had 176 seats then and 193 now, and 89% of them were filled against 84%.

CO2 per passenger was 123 kg in 2019 and 119 kg in 2025, down 3.7%. Fuel burned per flight was up 0.4% (1,972 gallons to 1,979) and passengers per flight were up 4.2% (156 to 163). The distance flown was about the same (869 miles then, 869 now).

United Airlines led in both years, with 57% of passengers in 2019 and 61% in 2025. Spirit Airlines no longer reaches 1% of passengers, having had 6% in 2019.

Airline by airline, Frontier Airlines went from 105 kg to 98 kg per passenger (180 seats per flight to 209, main aircraft Airbus A320neo in both years); Southwest Airlines went from 127 kg to 127 kg per passenger (155 seats per flight to 165, main aircraft Boeing 737-700 then and Boeing 737 MAX 8 now).

Denver to Houston, 2019 and 2025
Measure20192025
Passengers (thousands)2,1662,250
Flights (thousands)13.913.8
Seats filled89%84%
Gallons of fuel per flight1,9721,979
kg CO2 per passenger123119
CO2 per passenger by airline, 2019 and 2025, Denver to HoustonBar chart of kilograms of CO2 per passenger on Denver to Houston for each major airline in 2019 and in 2025.050100United Airlines 2019125 kgUnited Airlines 2025119 kgSouthwest Airlines 2019127 kgSouthwest Airlines 2025127 kgFrontier Airlines 2019105 kgFrontier Airlines 202598 kg
CO2 per passenger by airline, 2019 and 2025, Denver to HoustonBar chart of kilograms of CO2 per passenger on Denver to Houston for each major airline in 2019 and in 2025.050100United Airlines 2019125 kgUnited Airlines 2025119 kgSouthwest Airlines 2019127 kgSouthwest Airlines 2025127 kgFrontier Airlines 2019105 kgFrontier Airlines 202598 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 Houston and back: time in the air

Flights from Houston to Denver spent 125 minutes in the air on average in 2025, against 115 minutes from Denver to Houston: 10 minutes longer, 9% 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 166 gallons per flight, which is about 1.0 gallons or 10 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
Houston to Denver125.36,888
Denver to Houston115.26,947

Fly or drive

Driving is about 1,017 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 302 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 154% more than the 119 kg for a passenger on the flight.

With 3 people in the car, driving comes out lower per person than the flight (101 kg each, and 75 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 401 kg per vehicle.

CO2 per person by way of travel, Denver to HoustonBar chart of kilograms of CO2 per person flying, driving or taking the train between Denver and Houston.0100200300Flight, average119 kgCar, driver alone302 kgCar, 2 people151 kgCar, 4 people75 kg
CO2 per person by way of travel, Denver to HoustonBar chart of kilograms of CO2 per person flying, driving or taking the train between Denver and Houston.0100200300Flight, average119 kgCar, driver alone302 kgCar, 2 people151 kgCar, 4 people75 kg
CO2 per person, Denver to Houston. 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 milesSan Francisco to Denver136 kg CO2 per passenger over 960 milesChicago to Denver129 kg CO2 per passenger over 890 milesNew York to Denver213 kg CO2 per passenger over 1,616 milesLos Angeles to Atlanta261 kg CO2 per passenger over 1,937 milesChicago to Miami161 kg CO2 per passenger over 1,187 milesOrlando to Philadelphia118 kg CO2 per passenger over 861 milesAtlanta to Denver165 kg CO2 per passenger over 1,199 miles

Airports on this route: Denver International Airport, George Bush Intercontinental Airport, William P. Hobby 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.