Operation Blue Skies, a £5M UK trial, will use AI to tweak flight paths over the North Atlantic and cut the warming vapour trails jets leave behind.
Those white streaks jets leave across the sky aren’t harmless. Persistent contrails trap outgoing heat and account for roughly a third of aviation’s total climate impact. A new UK-backed trial wants to find out whether AI can quietly shrink that number.
Operation Blue Skies, a £5 million, 30-month programme backed by the UK government, brings together the University of Cambridge, Google, the Department for Transport, the Met Office, NATS, Contrails.org, and Imperial College London. It’s the world’s first airspace-wide trial of AI-driven flight path adjustments aimed at avoiding contrail formation.
Why Contrails Matter More Than They Look
Contrails form when water vapour in jet exhaust condenses and freezes around soot and other particles in the cold, humid air of the upper atmosphere. Most contrails vanish quickly, but persistent ones linger and trap outgoing heat, a warming effect that adds up to roughly one-third of aviation’s total climate footprint.
The trial will run across NATS-controlled Shanwick oceanic airspace, the eastern half of the North Atlantic corridor. Atmospheric modelling shows this single stretch of airspace accounts for roughly 5% of global contrail warming, with much of that concentrated during the winter months between November and February.
Small Altitude Tweaks, Tested at Scale
Operation Blue Skies will target that specific high-impact winter window using AI models to pinpoint exactly where and when altitude adjustments would do the most good. The trials involve minor, standard altitude changes within normal flight operations, coordinated entirely through established Air Traffic Control communication channels.
Testing will run primarily during the winter windows of 2026-2027 and 2027-2028, with roughly 20 to 40 test days planned per winter, scheduled during periods of lower air traffic. Researchers from Cambridge and Imperial College London will independently verify the trial’s climate outcomes.
Professor Steven Barrett, Regius Professor of Engineering at the University of Cambridge, called the project a major step forward: “Contrail avoidance could drastically reduce the global climate impact of aviation, at minimal cost to passengers and companies. Operation Blue Skies is a big step forward in this process, as it will test the ability of the UK to reduce contrail coverage at an airspace-wide scale and in a real-world setting.”
Government Money, Corporate Expertise
The trial sits alongside other UK government investments in aviation decarbonisation, including a separate £219 million commitment to boost domestic green fuel production. To keep public money focused on national scientific capability, all of the government grant funding for Operation Blue Skies goes directly to academic, non-profit, and aviation partners, rather than corporate partners.
Google is contributing £1.4 million in-kind through AI research expertise, engineering time, and high-performance computing infrastructure. Keir Mather, UK Minister for Aviation, Maritime and Freight, framed the trial as a matter of national leadership: “This is a world-first, and it’s British ingenuity leading the way. By testing small tweaks to flight paths over the Atlantic, we can cut the vapour trails left behind by planes.”
Kemal Armada, a Product Manager at Google, described the trial as a test of feasibility at scale rather than of the underlying science: “The question is no longer whether we can mitigate contrails, but whether we can make that mitigation work at the scale of the global aviation system.”
What Happens Next
Contrails.org is working alongside the consortium to connect the scientific and operational sides of the trial, integrating weather forecasts, shaping trial parameters, and supporting the data analysis needed to test whether contrail avoidance is safe, measurable, and practical across a busy stretch of oceanic airspace.
If the winter trials show that AI-guided altitude adjustments can meaningfully cut contrail formation without disrupting normal flight operations, it could offer airlines a relatively low-cost lever for cutting their climate impact, on top of costlier fixes like new aircraft or alternative fuels.