Contrail avoidance gets a budget: a £5m trial to see if AI forecasts can move aircraft

A £5m UK trial will test whether AI can help by predicting where warming contrails are likely to form and getting planes to avoid those areas.

The 30-month Operation Blue Skies project brings together Google, the UK government, the Met Office, air traffic control provider National Air Traffic Services (NATS) and academic researchers.

Dr Paul Hodgson, Google's technical lead for Operation Blue Skies, told the BBC's Tech Life programme: "We think that contrail warming is responsible for something like a third of all aviation climate warming."

Google will use satellite images and flight data to identify where planes have previously produced contrails, then combine this with weather patterns to forecast where conditions for new contrails are likely to occur.

The information will be passed to NATS, where air traffic controllers can direct pilots to avoid those areas.

Rather than dramatically changing a flight's route, the trial will mostly involve changing an aircraft's altitude by around 2,000ft, something which already happens routinely to avoid turbulence and bad weather, so passengers are unlikely to notice.

Ian Jopson, director of sustainability at NATS, said it should be "pretty much business as usual using existing procedures for the operators on the North Atlantic".

Testing will take place during selected evenings and nights in the winters of 2026-27 and 2027-28, when air traffic is lower.

Previous airline-level trials have achieved reductions of around 60-70% in contrail formation or warming, according to Hodgson.

The results of Operation Blue Skies are expected to be published in academic literature and opened to wider scientific scrutiny.

Contrails are made when hot exhaust from aircraft engines meets cold air at high altitude, creating ice crystals; many disappear quickly, but in particularly cold and humid conditions they can persist and spread, forming clouds which trap heat that would otherwise escape from the Earth.

Aviation Minister Keir Mather said the project would test "small tweaks to flight paths over the Atlantic" which could help make flying cleaner, and said: "This is a world-first, and it's British ingenuity leading the way."

Changing the altitude of an aircraft can mean it burns more fuel.

Hodgson said previous trials suggested the additional fuel use was 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 magnitude to all of the CO2 of aviation."

Modelling for Operation Blue Skies suggests a full deviation through Shanwick would mean around 100kg of additional fuel per affected aircraft.

Google is one of many big tech companies spending billions on new data centres, the power-hungry banks of computer chips which power AI, which environmentalists are concerned will contribute even more to climate change.

The project comes as the government backs expansion of UK airports, raising the wider question of whether tech solutions can sufficiently reduce aviation's environmental impact as demand for flying grows.

The Department for Transport's £2.65m plus Google's £1.4m totals £4.05m, leaving about £950,000 of the stated £5m not attributed to a named funder in the source.

If Shanwick accounts for about 5% of global contrail warming and contrail warming is about one third of aviation climate warming, the airspace corresponds to roughly 1.7% of aviation's total climate warming.

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.

For 100kg of extra fuel to represent less than 1% of a flight's fuel burn, that flight must burn more than about 10 tonnes of fuel.