Every Layover, Ranked by Carbon Cost (2026)

Direct flights emit less CO₂ than the same trip with a layover. Sometimes a lot less. Takeoff and climb burn the most fuel of any phase of flight, so when you swap a single nonstop for a connection, you're paying a fuel tax for the extra takeoff — on top of any detour distance.

We computed the carbon penalty for 30 popular long-haul routes where you could fly direct but a connecting alternative also exists. The result: choosing the layover instead of the nonstop adds an average of 5% more CO₂ per passenger — and on the worst route, New York (EWR) to Johannesburg (JNB), it's 12% more, an extra 144 kg of CO₂.

The numbers, ranked

Each row below is a real route with at least one nonstop carrier and a 1-stop alternative through a hub. We took the shortest available 1-stop and compared it to the direct. Always pick the row labelled “Direct” if you can.

What stands out

Why layovers cost more carbon

A flight burns fuel unevenly. The most intense phase is takeoff and the climb to cruise altitude — the engines run near maximum thrust, fighting gravity. Once the plane levels off, fuel burn per kilometre drops sharply.

A 1-stop trip forces the plane (or rather, two planes) through that high-burn phase twice. Even if the total distance through the hub is identical to the nonstop — which it almost never is — the extra takeoff alone adds around 25 kg of CO₂ per passenger. Add the inevitable detour distance and the penalty grows.

The Climate Action Accelerator specifically recommends choosing nonstop flights as one of the highest-impact ways to lower the carbon footprint of a given trip. It's also faster, cheaper on time, and easier on luggage.

How we calculated this

CO₂ emissions per passenger were estimated using ICAO methodology with three distance bands — short, medium, and long-haul — reflecting the lower per-km fuel burn of long flights at cruise. Layover trips add a fixed ~25 kg penalty for the extra takeoff/climb cycle on top of the per-leg figures.

The "cheapest 1-stop" for each route is the connection through whichever hub gives the shortest total flight distance, picked from real routes in our database. Even when the layover hub sits almost on the great-circle path between origin and destination — so the total km is barely longer than direct — the extra takeoff cycle adds about 25 kg of CO₂ per passenger.

These are economy-class, per-passenger figures — business and first class roughly double or triple the per-seat CO₂ because of how much cabin floor area each seat occupies. Cargo and crew are ignored.

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