Flight

What is the carbon footprint of a flight?

A return flight across the Atlantic emits over a tonne of CO2e per economy passenger. How flight emissions are calculated, what non-CO2 effects add, and how to cut them.

By Surya Narayanan · · 3 min read · How flying works

A return economy flight between New York and London puts out about 1.30 t of CO2-equivalent per passenger, by the UK government's published factors, once you include the extra warming that planes cause at altitude. In business class it's about 3.76 t. How big a flight's footprint is depends mostly on the distance, the cabin, and how the non-CO2 effects are counted.

How it's calculated

Most calculators, including ours, multiply the distance flown by an emission factor: the average greenhouse gas per passenger for each kilometre. We use the factors the UK Department for Energy Security and Net Zero (DESNZ) publishes each year for company reporting, the set most carbon calculators draw on. They come in three bands (short domestic hops, short-haul up to 3,700 km and long-haul), with separate figures for each cabin, and they already allow for the extra distance real flights fly beyond the great circle.

CO2 and the rest

Burning jet fuel releases CO2, but at cruising altitude planes also emit nitrogen oxides and water vapour and create contrails, all of which add warming. Scientists are less certain about the size of these non-CO2 effects than about CO2's, but they're not small. DESNZ counts them by multiplying the CO2 by 1.7; on that basis, the CO2 alone of a return transatlantic economy trip is about 763 kg. When you compare calculators, check whether they include non-CO2 effects, because that alone can nearly double the number.

What changes your footprint

  • Distance. The obvious one. Long-haul flights have a lower footprint per kilometre, but they cover so many kilometres that they dominate most people's flying emissions.
  • Cabin. A business seat takes up several times the space of an economy seat and so gets a bigger share of the fuel: about 2.9 times economy on long-haul flights by the government factors, and 4 times in first.
  • Short flights. Take-off and climb burn a lot of fuel. Per kilometre, London to Paris (348 km, about 80 kg one way) is worse than New York to London (648 kg one way for 5,540 km).
  • The aircraft and load. Newer jets and fuller planes mean less per passenger.
  • Nonstop versus connections. A connection adds a take-off and often some distance.

Cutting it

  1. Fly less, stay longer. One long trip instead of two short ones.
  2. Take the train for short trips where you can; rail produces a small fraction of the emissions of flying the same distance.
  3. Fly economy and nonstop.
  4. Pack light. Weight means fuel.
  5. Be careful with offsets. Their quality varies widely, and investigations in recent years have found that many offset projects claimed far more benefit than they delivered. Reducing flights does more than offsetting them.

Check your own flights

The flight carbon calculator works out any route, cabin and number of passengers, one way or return. For the distance alone, use the flight distance calculator. And the greenest flight of all is the one in Flight: a focus session as long as the real trip, flown entirely at your desk.

Questions

How much CO2 does a flight produce per passenger?

It depends on distance and cabin. By the UK government's factors, including non-CO2 effects, a one-way economy flight between New York and London is about 650 kg of CO2-equivalent per passenger, and a return trip about 1.3 tonnes.

Is flying worse than driving?

Per passenger-kilometre, flying is often comparable to driving alone in a typical car, but flights cover far greater distances, so a single long-haul trip can exceed months of driving. Trains are usually far lower than both.

Do carbon offsets work?

Some do, but quality varies widely, and investigations in recent years have found many projects claimed more benefit than they delivered. Flying less, flying economy and choosing nonstop flights reduce emissions more reliably.

Why is business class worse for the environment?

Because a business seat takes up much more space than an economy seat, it's allotted a larger share of the plane's fuel and emissions: roughly three times economy on long-haul flights by government factors.

Try it with a free tool

Keep reading

  1. The longest flights in the world, by distanceThe longest nonstop flights cover over 14,000 km and last up to 19 hours. Ten of the longest routes of recent years, ranked by distance, and what makes them possible.
  2. How long are flights? 30 popular routes timedFlight times for 30 popular routes across the Atlantic, North America, Europe, Asia and long-haul, with distances and time differences, and why schedules vary.
  3. Why flying east is faster than flying westEastbound flights ride the jet stream; westbound ones fight it. How strong it is, how much time it can save, and why it isn't the Earth's spin.
  4. Why flight paths look curved on a mapPlanes fly great circles, the shortest paths on a sphere, which look curved on flat maps. Why, how much longer a 'straight' route would be, and why real tracks differ.