What impact do you make on the environment when you fly?

How much gas does it take to fly you?

This is a question a lot of people probably don’t think about. After all, you’re (on average) 150 pounds, and the plane you’re flying on seems just way bigger. But this is actually an important question when it comes to discussing carbon footprint. Every additional passenger costs something. Let’s figure out how much it really is.

Flying a Boeing 737 from New York to Phoenix

The Boeing 737 is the most common jet airplane in the world. For our example here I’m going to use one type of Boeing 737, the 737-700. A full 737-700, including 180 passengers (and I assume .5 checked bags and one carry-on per passenger), can fly 4,300 miles (New York to Phoenix roundtrip) on 6,900 gallons of fuel. An empty one can fly nearly 8,000.

These 180 passengers, plus all their bags, weigh about 35,000 pounds, and the plane itself with all of these people and bags on board weighs 155,000 pounds. Therefore the empty plane with full fuel weighs 120,000 pounds. So let’s calculate:

Total passenger and bag weight: 35,000 pounds

Total passengers: 180

Range of full plane: 4,300 miles

Range of empty plane: 8,000 miles

Fuel needed to fly full plane roundtrip NYC to PHX: 6,900 gallons

Fuel needed to fly empty plane same distance: 6,900*(4,300÷8,000) = 3700 gallons

Additional fuel needed to fly full plane: 6,900-3,700 = 3,200 gallons

Additional fuel needed per passenger and their bags: 3,200 ÷ 180 = 18 gallons

Current price of A-1 jet fuel: $6.42/gallon

Cost per passenger to fly roundtrip New York to Phoenix: 18*6.42 = $115.56

Cost per passenger per mile: 115.56 ÷ 4,300 = 2.7 cents

Cost per pound to fly roundtrip: 3,200 ÷ 35,000 * 6.42 = $0.59

Environmental impact of a flight

Now, this last calculation showed us that there is a significant dollar cost to an airline to fly you instead of an empty seat. But what about the environmental impact you cause by flying? According to the Department of Energy, an airplane emits 21 pounds of carbon dioxide per gallon of A-1 jet fuel it burns. If we need 6,900 gallons to fly a full plane roundtrip New York to Phoenix, that’s an emission of nearly 145,000 pounds of carbon dioxide. Let’s break that down per pound of variable weight on the airplane (passengers and bags):

Total carbon emission for roundtrip flight: 145,000 pounds

Carbon emission per passenger: 145,000 ÷ 180 = 806 pounds

Carbon emission per passenger per mile:  806 ÷ 4,300 = .19 pounds

Carbon emission per pound of airplane weight per mile: 145,000 ÷ 155,000 ÷ 4,300 = .0002 pounds

Let’s wrap our heads around this. Every mile you fly, 3 ounces of carbon are released into the air. Last year, as a student at Wash U and a resident of Boston, I flew back home 5 times. At 2,000 miles roundtrip, I flew 10,000 total miles just for school. So I released nearly 2,000 pounds of carbon into the atmosphere. That is not insignificant.

As someone who cares about the environment, my impact on it is important to me. But the issue at hand is how we might make impacting the environment important to the airlines. It often seems like a daunting task to make a corporation care about the social externalities it creates, but in the case of the airlines it is a simple task of demonstrating the dollars and cents of reducing environmental impact.

For every mile a full 737-700 flies, 34 pounds of carbon are released into the air, or .0002 pounds per pound of airplane. More importantly to an airline, every mile flown costs $10.30, or $0.000066 (6.6 thousandths of a cent) per pound of airplane.

Let’s say this airplane flies this roundtrip once a day, for 365 days a year. The total cost for the year in fuel per pound of airplane would be $104. By reducing the weight of an airplane by one pound this year, an airline could save $104. And it could save the environment 314 pounds of CO2. Imagine the things an airline could remove from an airplane to save one pound. That’s about 4 in-flight magazines. Or 2 soda cans. The possibilities are endless.

American Airlines has 600 planes in its fleet. Granted, they’re not all 737s, and they don’t all fly the same distance, but let’s assume for simplicity’s sake that they did. If American removed one pound from each of its planes, it would save $62,000 a year. That’s not a small amount in a low-margin business. And more importantly for all the environmentalists out there, it would also save 190,000 pounds of carbon dioxide from the atmosphere.

So, next time you fly, ask yourself if you really need that one extra shirt. You can make more of a difference than you think.