The familiar white trails left by aircraft in the sky, known as contrails are more than just a picturesque sight. These icy clouds contribute significantly to climate change, accounting for roughly one-third of aviation’s total climate impact. Now, a groundbreaking trial called Operation Blue Skies is exploring how artificial intelligence can help mitigate this environmental challenge.
The £5 million project, led by Google and backed by the UK government will focus on the Shanwick Oceanic airspace in the eastern North Atlantic corridor. This region is responsible for approximately 5% of global contrail warming, making it a critical area for intervention. The trial will run during selected evenings and nights in the winters of 2026-27 and 2027-28, when air traffic is lower.
The science behind contrails and their climate impact
Contrails or condensation trails, form when the hot exhaust from aircraft engines meets the cold air at high altitudes, creating ice crystals. While many of these trails dissipate quickly, others persist and spread, forming clouds that trap heat and contribute to global warming. The Operation Blue Skies project aims to address this issue by predicting where these warming contrails are likely to form and adjusting flight paths accordingly.
Dr. Paul Hodgson, Google’s technical lead for the operation, explains that contrail warming is responsible for a significant portion of aviation’s climate impact. ‘We think that contrail warming is responsible for something like a third of all aviation climate warming,’ he said. The project also raises broader questions about whether technological solutions can sufficiently reduce aviation’s environmental impact as demand for flying continues to grow.
How AI will optimize flight paths to reduce contrails
The trial will use AI models to identify areas of the atmosphere where contrails are likely to form. Google will analyze satellite images and flight data to pinpoint where planes have previously produced contrails. This information will then be combined with weather patterns to forecast where new contrails are likely to occur.
The data will be passed to National Air Traffic Services (NATS) where air traffic controllers can direct pilots to avoid these areas. Rather than dramatically changing the route of a flight, the trial will mostly involve adjusting an aircraft’s altitude by around 2,000 feet. This is a routine practice to avoid turbulence and bad weather, so passengers are unlikely to notice any significant changes.
Ian Jopson, director of sustainability at NATS, assures that the adjustments will be ‘pretty much business as usual using existing procedures for the operators on the North Atlantic.’ Around 10,000 flights are expected to pass through the airspace during the trial periods, although only a fraction will need to change altitude specifically to avoid contrails.
Assessing the environmental benefits and challenges
One of the key questions surrounding the trial is whether avoiding contrails could lead to additional carbon emissions. Changing the altitude of an aircraft can mean it burns more fuel. However, Dr. Hodgson notes that previous trials suggested the additional fuel use is much smaller than the climate benefit of preventing a warming contrail. ‘The CO2 penalty is in the order of less than 1%, compared to the contrail cost, which is of a similar order of magnitude to all of the CO2 of aviation,’ he said.
Modelling for Operation Blue Skies suggests that a full deviation through the Shanwick airspace would mean around 100kg of additional fuel per affected aircraft. Previous airline-level trials have achieved reductions of around 60-70% in contrail formation or warming. The results of the trial are expected to be published in academic literature and opened to wider scientific scrutiny.
Aviation Minister Keir Mather highlighted the innovative aspect of the project, stating that it would test ‘small tweaks to flight paths over the Atlantic’ which could help make flying cleaner. ‘This is a world-first, and it’s British ingenuity leading the way,’ he said. The trial represents a significant step forward in the quest to reduce aviation’s environmental impact and could provide a blueprint for similar initiatives in other regions.
