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The tests, due to start in late 2026, will involve flights over the North Atlantic. Led by Google, backed by the UK government and involving the Met Office, Imperial College London and the University of Cambridge, the project will investigate whether small, AI-guided flightpath adjustments could reduce aeroplane contrails.
Formed due to soot released during fuel combustion, contrails and the cirrus clouds they create could account for more than half (57%) of aviation’s climate impact, according to a 2021 study published in Atmospheric Environment.
Imperial experts in atmospheric science and aerospace engineering will test the theory that altering the altitude at which planes fly can reduce warming from aircraft contrails across the North Atlantic.
Known as Operation Blue Skies, the project will use AI models to identify when and where small altitude adjustments could reduce warming from contrails, specifically focusing on the Shanwick Oceanic airspace to the north-west of Ireland, controlled by air traffic control company Nats.
Atmospheric modelling suggests that Shanwick airspace accounts for approximately 5% of global contrail warming. Much of this occurs during evening hours between November and February, making the region an ideal place to test the approach.
In the winters of 2026 and 2027, when contrails are most prevalent, airlines flying in the area will alter their flight paths in line with the trial, and scientists at Imperial and Cambridge will measure the impact.
The project builds on research led by Imperial scientists, who demonstrated in 2020 that changing the altitude of fewer than 2% of flights could reduce contrail-related climate warming by 59%. Operation Blue Skies provides the first opportunity to test that concept in a major transatlantic airspace region under real-world operating conditions.
“This project is an opportunity to advance both understanding and capability in aviation sustainability. Navigational contrail avoidance has been receiving growing attention, but we need empirical proof that the tools we have available to us are up to the challenge,” said Dr Sebastian Eastham, associate professor in sustainable aviation at Imperial.
“One big question in this regard is whether model-based predictions of contrail formation are accurate enough far enough in advance, [so] that we can then successfully navigate to avoid contrail-forming regions. Operation Blue Skies brings together the pieces needed to do just that, using satellite imagery to monitor whether the predicted benefits actually materialise when we perform small flight plan adjustments based on contrail formation predictions.”
The first operational trial is expected to take place during the winter of 2026-27, with a second in winter 2027-28. Changes to flight paths will be “incremental and barely noticeable to passengers”, according to an Imperial announcement, requiring only small adjustments to aircraft altitude.
“Both the weather and global aviation are hugely complex systems, making contrail avoidance a challenging task. This trial is an important step forward, testing how these systems can work together at a large scale,” said Dr Edward Gryspeerdt, associate professor in atmospheric physics at Imperial.
“It is very exciting to see how scientific research on aviation, clouds and satellite remote sensing can be used to address climate change and build a more sustainable future.”
Operation Blue Skies is co-funded by its industry partners and the Department for Transport through the ATI Programme, a partnership between the Aerospace Technology Institute, the Department for Business, Innovation, Science and Trade, and Innovate UK.
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