Planes flying across the North Atlantic Ocean later this year will be re-routed to avoid causing condensation trails, in a first-of-a-kind trial to address the global warming impact of contrails across an entire airspace.
Starting in November, air traffic controllers managing the Shanwick airspace on the eastern side of the North Atlantic will advise planes to adjust their altitude to avoid creating fresh contrails. The controllers will be using AI-generated forecasts of atmospheric conditions from Google that predict where contrails will form.
āWe can predict the regions that are going to form persistent climate-warming contrails, and we can re-route planes around them,ā at Contrails.org, a research organisation that is participating in the project, said during a press briefing on 17 August.
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Contrails are formed when soot particles emitted by jet engines trigger the formation of ice particles, leaving a condensation trail that can last for hours. During the day, these persistent contrails help to reflect solar radiation back to space, which has a cooling effect. But they also trap heat below them, causing warming. Overall, contrails are thought to account for around one-third of aviationās climate impact.
The Shanwick airspace is a contrail hotspot and a busy area for planes crossing the North Atlantic. suggests the airspace is responsible for about 5 per cent of global contrail warming, and most of this effect occurs during the winter season between November and February.
The Ā£5 million Operation Blue Skies project will re-route flights in the evening and night, which have the biggest warming effect. Pilots entering the Shanwick airspace will be instructed to adjust their altitude by up to 2000 feet (600 metres) to avoid atmospheric conditions where contrail formation is likely. The advice will be issued under the same procedures already used by air traffic controllers to help pilots avoid turbulence or other weather conditions.
The trial will run during two four-month winter trials over 2026-2027 and 2027-2028, with approximately 20 to 40 test days during each winter season. Around 10,000 flights are expected to pass through the airspace during trial hours each year, and hundreds will need to be re-routed to produce a statistically significant data set for analysis. Researchers from the University of Cambridge and Imperial College London will analyse the data from the trial.
The climate benefit of avoiding contrails is worth any extra fuel burn from shifting flight paths, at Google UK said during the briefing. Re-routed flights may have to burn an additional 100 kilograms of fuel per aircraft while crossing the airspace, resulting in an additional few hundred kilograms of CO2 emitted. By comparison, āthe contrail impact on those flights, especially at those times of day, is measured in the tonnes or even the tens of tonnesā, he said.
The project follows previous trials of Googleās AI contrail forecasts, which have been used to inform airlinesā flight plans before take-off and routes set by air traffic dispatchers. This work suggests re-routing a plane can cut contrail formation by 50 to 60 per cent.
But this is the first time contrail forecasts will be used across an entire airspace, and airlines will not be able to opt out. āThis is what we call an airspace-scale trial, where deviations will effectively be instructed from the air traffic controller and affect all of the aircraft that are flying in this particular region,ā said Hodgson.
