Flying warms the planet in more ways than CO₂. Contrails and NOx add a lot of warming, but no one pays for it yet. This page shows what that warming is, why it comes as a range, and what the EU is doing about it.
Today, contrails and NOx cause about two thirds of the warming from flying. CO₂ causes about a third.
EU ETS, UK ETS and CORSIA only price CO₂. The rest of the warming is free, for now.
Since 1 January 2025, flights in the EU scheme have their non-CO₂ effects tracked. A decision on what comes next is due by the end of 2027.
Share of warming: Lee et al. (2021), effective radiative forcing for 2018.
A contrail is a line of ice behind a plane. Most fade in seconds. The ones that matter form in very cold, humid air, spread into thin cloud and last for hours. Try it below.
The ice fades in seconds to minutes. There is little or no effect on the climate.
of flights cause about 80% of contrail warming. They are mostly long, high, night-time flights. So changing the height or route of a small number of flights could cut most of it.
Teoh et al. (2020, 2024).
To put non-CO₂ warming in the same units as CO₂, studies use a multiplier: for every tonne of CO₂ a flight makes, how many tonnes of "CO₂-equivalent" warming it really causes. Three well-known estimates disagree.
No rule prices non-CO₂ today. But if it were priced the same way as CO₂, this shows roughly how much more a fleet would pay.
This is a "what if", not a forecast. If the EU does price non-CO₂, it may use its own per-flight method instead of one multiplier for every flight. That could be much higher for some routes and close to zero for others.
Airlines in the EU scheme must monitor, report and verify non-CO₂ effects. The EU estimates them for each flight from flight data, the plane, the fuel and the weather.
The EU plans to set aside up to 3 million free allowances up to 2033, with no more than 420,000 a year, shared between airlines in the scheme (about €33.6m a year at today's price). Airlines would get them for planning flights around contrails and for better reporting. It is only a plan for now.
The European Commission reports on what the tracking found and, if it sees fit, proposes a law to deal with non-CO₂ effects. That could mean bringing them into the EU carbon market.