UK Trials AI System to Reroute Flights Around Warming Contrails

A new UK-led initiative will test whether artificial intelligence can reduce aviation's climate impact by helping aircraft avoid creating persistent contrails—the white vapor trails that contribute significantly to global warming.

Operation Blue Skies, a £5 million, 30-month trial, brings together Google, the UK government, the Met Office, National Air Traffic Services, and academic researchers to tackle what scientists estimate accounts for roughly one-third of aviation's total climate warming effect, according to details first reported by the BBC.

The project will focus on Shanwick Oceanic airspace in the eastern North Atlantic corridor, which handles approximately 5% of global contrail warming.

How the system works

Contrails form when hot aircraft exhaust meets cold air at high altitude, creating ice crystals. While many dissipate quickly, those forming in particularly cold and humid conditions can persist for hours, spreading into cirrus-like clouds that trap heat radiating from Earth's surface.

Google will analyze satellite imagery and flight data to identify where aircraft have previously produced contrails, then combine this information with weather patterns to forecast atmospheric conditions likely to generate new warming contrails. Air traffic controllers at NATS will use these predictions to direct pilots around problem areas—typically by adjusting altitude by around 2,000 feet rather than changing horizontal flight paths.

Dr. Paul Hodgson, Google's technical lead for the project, told the BBC that while uncertainty exists around precise figures, scientists are confident contrail warming represents "either quite a large problem or a very large problem."

Testing parameters and fuel trade-offs

The trial will run during selected evenings and nights in the winters of 2026-27 and 2027-28, when air traffic volumes are lower. Around 10,000 flights are expected to pass through the airspace during testing periods, though only a fraction will need altitude changes specifically to avoid contrails.

A critical question is whether the additional fuel burned by altitude changes negates climate benefits. Hodgson said previous trials suggest the fuel penalty is less than 1%, while the contrail climate cost approaches the magnitude of aviation's total CO2 emissions. Modeling for Operation Blue Skies indicates full deviations through Shanwick would require roughly 100kg of additional fuel per affected aircraft.

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

Why it matters

As governments back airport expansion—including the UK's recent support for growth—the aviation industry faces mounting pressure to demonstrate that technological solutions can offset increased environmental impact from rising flight demand. This trial represents one of the first large-scale attempts to operationalize contrail avoidance using AI prediction, potentially offering a near-term mitigation strategy that doesn't require new aircraft designs or alternative fuels. Success could establish a model for implementation across other high-traffic airspaces worldwide.

The Department for Transport is providing £2.65 million toward the program, while Google is contributing £1.4 million through AI research, engineering, and computing infrastructure. Ian Jopson, director of sustainability at NATS, said the changes should be "pretty much business as usual using existing procedures" that pilots already use to avoid turbulence and weather.

Results are expected to be published in academic literature for wider scientific scrutiny. The BBC first reported details of the Operation Blue Skies trial.