TL;DR
A £5m British project running 30 months will find out whether AI can forecast where climate-warming contrails form and route aircraft around them. Operation Blue Skies covers the eastern North Atlantic’s Shanwick Oceanic airspace, responsible for roughly 5% of contrail warming worldwide. The fix is small: shifting altitude by about 2,000ft.
The problem being targeted
Contrails form when hot engine exhaust meets cold air at altitude and freezes into ice crystals. Most vanish quickly. In cold, humid conditions they persist and spread into cloud that traps heat which would otherwise escape — and by Google’s estimate that effect accounts for perhaps a third of everything aviation contributes to warming.
Google’s technical lead on the project, Paul Hodgson, conceded uncertainty around the exact share while arguing the range itself is the point: scientists are confident it is “either quite a large problem or a very large problem”. His five-year-old, he told the BBC, calls the white lines “sky graffiti”.
How it would work
Google will combine satellite imagery with flight data to establish where aircraft have produced contrails before, then layer weather forecasting on top to predict where conditions will recur. That forecast goes to NATS, whose controllers can direct pilots around the affected air.
Crucially this is not rerouting. Altitude adjustments of around 2,000ft already happen routinely for turbulence and weather, so passengers should notice nothing. Ian Jopson, who directs sustainability at NATS, expects it to be “pretty much business as usual using existing procedures”. Testing runs on selected evenings and nights over two winters, 2026-27 and 2027-28, while traffic is lighter, with around 10,000 flights passing through and only a fraction needing to move.
The obvious objection — that climbing or descending burns more fuel — has been costed. Modelling puts the penalty at roughly 100kg of extra fuel per affected aircraft, which Hodgson frames as under 1% in CO2 terms against a contrail cost comparable to all of aviation’s carbon. Earlier airline trials cut contrail formation or warming by 60-70%.
Looking forward
Transport department funding runs to £2.65m, with Google adding £1.4m through research, engineering and computing. Keir Mather, the aviation minister, called it a world first and “British ingenuity leading the way”. Results are destined for academic publication and open scrutiny, which matters given every figure here originates with the participants. There is an awkwardness the BBC does not skate over: Google is spending heavily on the power-hungry data centres that AI requires, and the UK has just been told its universities cannot measure the emissions of their own AI rollouts. Measuring the benefit precisely while the cost stays vague is the recurring shape of AI-for-climate claims.