Travel · emission factor
The Carbon Footprint of Flying
255 g CO₂e / km
Air travel emits roughly 255 g CO₂e per passenger-kilometre, making it one of the most carbon-intensive ways to move a person — about 12 times the footprint of a train journey of the same distance. A single round-trip long-haul flight can add more to your annual footprint than months of everyday driving, which is why flights are often the largest single line item in a personal carbon budget.
Why flying is so carbon-intensive
Aircraft burn kerosene-based jet fuel, and each kilogram of it releases about 3.16 kg of CO₂. Take-off and climb are especially fuel-hungry, which is why short flights have a higher per-kilometre footprint than long ones — the energy-intensive phases are spread over fewer kilometres. On top of the CO₂ itself, burning fuel at cruising altitude produces nitrogen oxides, water vapour and contrails that add extra warming; scientific assessments estimate aviation's total warming effect is roughly two to three times its CO₂ alone. The 255 g figure is a per-passenger average that already accounts for typical occupancy: a fuller plane divides the same fuel burn among more people, while premium cabins take up more space per seat and carry a correspondingly larger share.
How flying compares with other transport
At 255 g CO₂e per passenger-kilometre, flying sits near the top of the transport ladder, just below cruise ships at 280 g and above a petrol car at 231 g (with a single occupant — carpooling changes the picture). The contrast with rail is striking: a train on a low-carbon grid emits around 20 g per passenger-kilometre, so a 500 km flight produces roughly 128 kg CO₂e versus about 10 kg by train. A bus averages 105 g and an electric car about 8 g per passenger-km on a clean grid. Globally, aviation accounts for about 2–3% of CO₂ emissions, but that share is concentrated among frequent flyers: most of the world's population does not fly in a given year.
What a real trip adds up to
Distance is what matters most. A short 1,000 km round trip — say Paris to Barcelona and back — comes to roughly 255 kg CO₂e per passenger. A transatlantic round trip of about 12,000 km reaches roughly 3 tonnes CO₂e, comparable to a year of driving 13,000 km in a petrol car. That scale explains why a handful of long-haul flights can dominate an otherwise low-carbon lifestyle. It also explains why the biggest levers are structural: choosing rail for trips under about 1,000 km, flying direct rather than via connections (each extra take-off adds fuel burn), and consolidating trips. Efficiency gains from newer aircraft help — modern jets burn 15–20% less fuel per seat than the generation they replace — but demand growth has historically outpaced them.
How plane compares
g CO₂e / km · data as used in the Decarbonr app · sources: European Environment Agency, IPCC
How to reduce this footprint
- ✓ Take the train for trips under about 1,000 km — it cuts the journey's emissions by roughly 90%.
- ✓ Fly direct when you must fly: take-off and landing are the most fuel-intensive phases, so avoiding connections avoids extra burn.
- ✓ Choose economy class — premium seats occupy more cabin space and carry a proportionally larger share of the flight's emissions.
- ✓ Combine trips or extend stays so one flight replaces two, and track your flights so you can see their real share of your yearly footprint.
Frequently asked questions
How much CO₂ does a flight emit per kilometre?
A typical flight emits about 255 g CO₂e per passenger-kilometre, averaged over normal occupancy. Short-haul flights tend to be somewhat higher per kilometre because take-off and climb burn a large share of the fuel, while long-haul cruise is more efficient per km.
Is flying worse than driving?
Per passenger-kilometre, flying at 255 g is slightly above a solo petrol car at 231 g — but flights cover far greater distances, so total trip emissions are usually much larger. A car with two or more occupants beats a plane per person, and a train at around 20 g/km beats both by a wide margin.
Do contrails really make flying worse for the climate?
Yes. Contrails and other high-altitude effects like nitrogen oxides add warming beyond the CO₂ itself; research estimates aviation's total climate impact at roughly two to three times its CO₂-only footprint. The 255 g figure covers CO₂-equivalent fuel emissions, so the full warming effect of a flight is likely higher.
Track this automatically
Decarbonr turns meals and journeys into one clear daily CO₂e number — on your iPhone, on-device, private by design.
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Sources & methodology: see Research & scientific references. Figures are averages used by the Decarbonr app; real-world values vary by production system, country, and occupancy.