A £5 Million AI Trial Wants to Stop Planes Drawing Heat-Trapping Lines Across the Sky

Key points

• The UK's Operation Blue Skies trial will run for 30 months starting in winter 2026, at a total cost of £5 million.
• Google is contributing £1.4 million in AI research, engineering and computing infrastructure; the Department for Transport is providing £2.65 million.
• The trial targets Shanwick Oceanic airspace in the eastern North Atlantic, a zone responsible for roughly 5% of global contrail warming.
• Previous airline-level trials have cut contrail formation or warming by 60 to 70%, according to Google's technical lead.
• Around 10,000 flights will pass through the trial airspace, though only a fraction will need to change altitude.

Those white streaks planes leave behind in a clear sky are not just pretty. They are contrails, thin trails of ice crystals that form when hot engine exhaust meets the freezing air at cruising altitude. In the right conditions, cold and humid air, they do not dissolve. They spread into wispy cloud layers that trap heat rising from Earth's surface, much like a blanket.

Scientists believe contrail warming accounts for roughly a third of all the climate damage caused by aviation. Google technical lead Dr Paul Hodgson, speaking to BBC Technology, put it plainly: it is "either quite a large problem or a very large problem."

What will the trial actually do?

The plan is straightforward: predict where contrails will form, then move planes out of the way before they get there. Operation Blue Skies will ask aircraft to change altitude by around 2,000 feet, a small shift that pilots already make routinely to avoid turbulence. Passengers will almost certainly not notice.

Google's role is to analyse satellite images and historical flight data to map where contrails have formed in the past. That information gets layered with live weather forecasts to predict danger zones. The predictions then go to National Air Traffic Services (NATS), the UK's air traffic control provider, whose controllers can redirect pilots accordingly.

Testing will run on selected evenings and nights during the winters of 2026-27 and 2027-28, when fewer planes are in the air. The focus area is Shanwick Oceanic airspace, the eastern half of the North Atlantic corridor.

Does dodging contrails just burn more fuel?

Yes, slightly. Changing altitude costs extra fuel, which means extra carbon dioxide. But previous trials suggest the trade-off strongly favours the detour. Dr Hodgson told BBC Technology that the extra fuel burn "is in the order of less than 1%" compared to the climate cost of a persisting contrail. Operation Blue Skies modelling puts the additional fuel per diverted aircraft at around 100 kilograms, a modest figure against the warming that a cloud-spreading contrail would otherwise cause.

Past airline trials achieved 60 to 70% reductions in contrail formation or warming, a figure that gives the project team confidence the approach works at smaller scales. Whether it holds across a major oceanic corridor is precisely what Operation Blue Skies is designed to find out.

Results will be published in peer-reviewed academic literature, meaning independent scientists will check the numbers before any wider policy decisions are made.

Common questions

Will this make flights more expensive?

The additional fuel per redirected flight is estimated at around 100 kilograms, a small fraction of a transatlantic tank. Airlines and the government have not announced any plan to pass that cost to passengers.

When will we know if it worked?

The trial runs across two winters, ending in early 2028. Results are expected to be published in academic journals shortly after, where they will face independent scientific review.

Does this fix aviation's full climate impact?

No. Contrails are one part of the picture. Jet fuel still produces carbon dioxide on every flight, and demand for air travel is growing. This trial addresses one specific, measurable problem; it does not replace the need for cleaner fuels or other measures.