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Rankings / Routes / Chicago to Houston

2025 flights

Chicago to Houston

Between Chicago and Houston, 2.2 million passengers flew nonstop in 2025, on 16 thousand flights of about 928 miles and 2.1 hours in the air. The average passenger accounted for about 134 kg of CO2 from the fuel burned, from 109 kg on Spirit Airlines to 213 kg on Republic Airways.

  • 134 kgCO2 per passenger, average
  • 928 milesabout 2.1 hours in the air
  • 2.2 millionpassengers in 2025
  • 83%of seats filled

CO2 per passenger, airline by airline

CO2 per passenger by airline, Chicago to HoustonBar chart of kilograms of CO2 per passenger on each airline between Chicago and Houston in 2025.050100150200Spirit Airlines109 kgFrontier Airlines117 kgSouthwest Airlines127 kgUnited Airlines128 kgAmerican Airlines196 kgRepublic Airways213 kg
CO2 per passenger by airline, Chicago to HoustonBar chart of kilograms of CO2 per passenger on each airline between Chicago and Houston in 2025.0100200Spirit Airlines109 kgFrontier Airlines117 kgSouthwest Airlines127 kgUnited Airlines128 kgAmerican Airlines196 kgRepublic Airways213 kg
Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.
Chicago to Houston by airline, 2025
AirlineShare of passengersFlights (thousands)Main aircraftSeats per flightSeats filledkg CO2 per passenger
United Airlines55%7.6Boeing 737-900ER, Airbus A321neo18984%128
Southwest Airlines23%3.6Boeing 737 MAX 8, Boeing 737-80016683%127
American Airlines8%1.6Airbus A319, Boeing 737-80013180%196
Spirit Airlines7%0.9Airbus A320-200, Airbus A321neo19487%109
Frontier Airlines5%0.7Airbus A320neo, Airbus A321neo19676%117
Republic Airways2%0.7Embraer 1757689%213

What explains the differences

It's number 58 of the 100 busiest city pairs by passengers, and number 35 for the lowest CO2 per mile flown (0.14 kg per passenger-mile, number 1 being the lowest). A typical route of 928 miles in this set comes out at about 143 kg, so this one is 6.1% below it.

The flights use more than one pair of airports: ORD to IAH (75%), MDW to HOU (23%), MDW to IAH (2%). The figures here cover all of them.

The airlines on this route differ by 95% per passenger. Spirit Airlines burned 1,893 gallons per flight and 169 passengers on each, and Republic Airways 1,475 gallons and 67 passengers. The gap comes from how many passengers share each flight, not from fuel burned per flight. Spirit Airlines flew 87% full here against 89% for Republic Airways, flying mostly Airbus A320-200 against Embraer 175.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 120 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 12% higher.

2019 compared with 2025

In 2019 the route carried 2.0 million passengers on 15 thousand flights. In 2025 it carried 2.2 million, up 12%, on 16 thousand flights, up 7%. The average flight had 160 seats then and 171 now, and 85% of them were filled against 83%.

CO2 per passenger was 147 kg in 2019 and 134 kg in 2025, down 9.2%. Fuel burned per flight was down 4.9% (2,054 gallons to 1,953) and passengers per flight were up 4.7% (136 to 142). The distance flown was about the same (928 miles then, 928 now).

United Airlines led in both years, with 49% of passengers in 2019 and 55% in 2025. Southwest Airlines lost the most, 28% to 23%. Frontier Airlines and Republic Airways didn't have 1% of the passengers in 2019 and now together carry 7%. Envoy Air no longer reaches 1% of passengers, having had 3% in 2019.

Airline by airline, United Airlines went from 152 kg to 128 kg per passenger (176 seats per flight to 189, main aircraft Boeing 737-900ER in both years); American Airlines went from 159 kg to 196 kg per passenger (154 seats per flight to 131, main aircraft Boeing 737-800 then and Airbus A319 now).

Chicago to Houston, 2019 and 2025
Measure20192025
Passengers (thousands)1,9732,207
Flights (thousands)14.515.5
Seats filled85%83%
Gallons of fuel per flight2,0541,953
kg CO2 per passenger147134
CO2 per passenger by airline, 2019 and 2025, Chicago to HoustonBar chart of kilograms of CO2 per passenger on Chicago to Houston for each major airline in 2019 and in 2025.050100150200United Airlines 2019152 kgUnited Airlines 2025128 kgSouthwest Airlines 2019138 kgSouthwest Airlines 2025127 kgAmerican Airlines 2019159 kgAmerican Airlines 2025196 kgSpirit Airlines 2019124 kgSpirit Airlines 2025109 kg
CO2 per passenger by airline, 2019 and 2025, Chicago to HoustonBar chart of kilograms of CO2 per passenger on Chicago to Houston for each major airline in 2019 and in 2025.0100200United Airlines 2019152 kgUnited Airlines 2025128 kgSouthwest Airlines 2019138 kgSouthwest Airlines 2025127 kgAmerican Airlines 2019159 kgAmerican Airlines 2025196 kgSpirit Airlines 2019124 kgSpirit Airlines 2025109 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.

Chicago to Houston and back: time in the air

Flights from Chicago to Houston spent 133 minutes in the air on average in 2025, against 125 minutes from Houston to Chicago: 8 minutes longer, 6% 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 910 gallons per flight hour, those extra minutes cost about 115 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
Chicago to Houston132.67,787
Houston to Chicago125.07,734

Fly or drive

Driving is about 1,086 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 322 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 141% more than the 134 kg for a passenger on the flight.

With 3 people in the car, driving comes out lower per person than the flight (107 kg each, and 81 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 428 kg per vehicle.

CO2 per person by way of travel, Chicago to HoustonBar chart of kilograms of CO2 per person flying, driving or taking the train between Chicago and Houston.0100200300Flight, average134 kgCar, driver alone322 kgCar, 2 people161 kgCar, 4 people81 kg
CO2 per person by way of travel, Chicago to HoustonBar chart of kilograms of CO2 per person flying, driving or taking the train between Chicago and Houston.0100200300Flight, average134 kgCar, driver alone322 kgCar, 2 people161 kgCar, 4 people81 kg
CO2 per person, Chicago 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

New York to Chicago125 kg CO2 per passenger over 730 milesLos Angeles to Chicago225 kg CO2 per passenger over 1,739 milesChicago to Washington, DC121 kg CO2 per passenger over 609 milesChicago to Denver129 kg CO2 per passenger over 890 milesSan Francisco to Denver136 kg CO2 per passenger over 960 milesDallas-Fort Worth to Miami160 kg CO2 per passenger over 1,119 milesDenver to Las Vegas91 kg CO2 per passenger over 628 miles

Airports on this route: O'Hare International Airport, George Bush Intercontinental Airport, Midway International 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.