Three ways to burn less

Picture a jet taking off from Heathrow for New York. It burns roughly 45 to 70 tonnes of fuel, depending on the plane and the wind. That is the whole story of its carbon: no filter, no catch, no clean-up. At the engine, less fuel is the only lever. What the fuel was made from is lesson 6.

Heathrow's plan names three ways airlines can burn less by 2030, each with a size. Fly straighter routes and sit on the runway less: up to 1 in 100. Replace old planes with newer ones that burn less per seat: up to 8 in 100. Change the fuel: up to 7 in 100. Together, up to 15 or 16.

Tap the lever Heathrow expects to cut the most by 2030.

Tap the part of the picture that answers it.

Newer planes burn less because of better engines, lighter bodies and more seats per flight. A new long-haul plane burns roughly a fifth to a quarter less fuel per seat than the one it replaces. Heathrow does not buy planes. It charges airlines less to land a cleaner one, which is how an airport moves smoke it does not own.

Move the control through the share of flights on newer planes. The figures are made up and round; the shape is the real thing. Each newer plane burns a quarter less per seat.

Move the control.

Straighter routes are the small lever, and the one Heathrow can touch most directly. Aircraft queue in the sky over London, can taxi for twenty minutes, and run engines at the gate for air conditioning. Plugging in at the gate, electric tugs to push back, and redrawn routes each shave a little. Together, up to 1 in 100.

Put the chain in order: from an airline's decision to Heathrow's count falling.

Tap them in the order they happen, first to last. Each tap gets a number.

• An airline retires a 25-year-old plane and buys a new one
• Every flight it makes from Heathrow turns less fuel into carbon
• Heathrow's in-the-air count falls, though the airport bought nothing
• The new plane burns a quarter less fuel per seat

By the end of 2025 the in-the-air count was 7 in 100 below 2019, and Heathrow puts that down to newer planes. The fuel lever is not yet in the count at all, because the rules for counting it are still being written. So the first half of the target arrived from one lever.

An airport serving mostly low-cost airlines with young fleets says its planes cannot get much cleaner. Which lever has it already mostly used?

• New fuel. Young planes already run on it.
• Straighter routes. Low-cost airlines fly direct.
• Newer planes. A young fleet has taken that saving; the next cut must come from routes or fuel.