Denver to Phoenix

Between Denver and Phoenix, 2.4 million passengers flew nonstop in 2025, on 18 thousand flights of about 602 miles and 1.4 hours in the air. The average passenger accounted for about 93 kg of CO2 from the fuel burned, from 72 kg on Frontier Airlines to 123 kg on American Airlines.

93 kgCO2 per passenger, average
602 milesabout 1.4 hours in the air
2.4 millionpassengers in 2025
77%of seats filled

CO2 per passenger, airline by airline

Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.

Denver to Phoenix by airline, 2025

Airline	Share of passengers	Flights (thousands)	Main aircraft	Seats per flight	Seats filled	kg CO2 per passenger
Southwest Airlines	41%	7.9	Boeing 737 MAX 8, Boeing 737-700	165	75%	95
United Airlines	29%	4.9	Boeing 737-800, Boeing 737-900ER	176	80%	93
Frontier Airlines	20%	2.8	Airbus A320neo, Airbus A321neo	209	81%	72
American Airlines	9%	1.9	Airbus A320-200, Boeing 737-800	164	70%	123

What explains the differences

It's number 49 of the 100 busiest city pairs by passengers, and number 53 for the lowest CO2 per mile flown (0.15 kg per passenger-mile, number 1 being the lowest). A typical route of 602 miles in this set comes out at about 103 kg, so this one is 9.2% below it.

The airlines on this route differ by 70% per passenger. Frontier Airlines burned 1,259 gallons per flight and 170 passengers on each, and American Airlines 1,454 gallons and 115 passengers. Fuel burned per flight explains about 27% of the gap and the number of passengers on each flight the other 73%. Frontier Airlines flew 81% full here against 70% for American Airlines, flying mostly Airbus A320neo against Airbus A320-200.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 78 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 20% higher.

2019 compared with 2025

In 2019 the route carried 2.2 million passengers on 15 thousand flights. In 2025 it carried 2.4 million, up 10%, on 18 thousand flights, up 17%. The average flight had 163 seats then and 173 now, and 88% of them were filled against 77%.

CO2 per passenger was 90 kg in 2019 and 93 kg in 2025, up 4.0%. Fuel burned per flight was down 2.9% (1,312 gallons to 1,273) and passengers per flight were down 6.7% (143 to 133). The distance flown was about the same (602 miles then, 602 now).

Southwest Airlines led in both years, with 46% of passengers in 2019 and 41% in 2025. Frontier Airlines gained the most share, 13% to 20%. American Airlines lost the most, 19% to 9%.

Airline by airline, Frontier Airlines went from 73 kg to 72 kg per passenger (187 seats per flight to 209, main aircraft Airbus A320neo in both years); American Airlines went from 97 kg to 123 kg per passenger (171 seats per flight to 164, main aircraft Airbus A321 then and Airbus A320-200 now).

Denver to Phoenix, 2019 and 2025

Measure	2019	2025
Passengers (thousands)	2,186	2,395
Flights (thousands)	15.3	18.0
Seats filled	88%	77%
Gallons of fuel per flight	1,312	1,273
kg CO2 per passenger	90	93

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 Phoenix and back: time in the air

Flights from Denver to Phoenix spent 90 minutes in the air on average in 2025, against 82 minutes from Phoenix to Denver: 8 minutes longer, 10% 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 887 gallons per flight hour, those extra minutes cost about 120 gallons per flight, which is about 0.9 gallons or 9 kg of CO2 for each passenger on the slower direction. The route figure above averages both directions.

Time in the air by direction, 2025

Direction	Average minutes in the air	Flights
Denver to Phoenix	90.1	8,949
Phoenix to Denver	82.0	9,012

Fly or drive

Driving is about 704 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 209 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 125% more than the 93 kg for a passenger on the flight.

With 3 people in the car, driving comes out lower per person than the flight (70 kg each, and 52 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 278 kg per vehicle.

CO2 per person, Denver to Phoenix. 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 miles Los Angeles to Phoenix74 kg CO2 per passenger over 354 miles San Francisco to Denver136 kg CO2 per passenger over 960 miles Chicago to Denver129 kg CO2 per passenger over 890 miles Atlanta to Boston143 kg CO2 per passenger over 939 miles Miami to Washington, DC144 kg CO2 per passenger over 921 miles Los Angeles to Seattle151 kg CO2 per passenger over 959 miles

Airports on this route: Denver International 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.