NATS has launched a £5 million programme to test whether small changes to aircraft cruising altitudes can reduce the climate-warming effect of persistent contrails over the North Atlantic.
Operation Blue Skies was announced on 18 August 2026 and will run for 30 months in NATS-controlled Shanwick oceanic airspace, which covers the eastern half of the North Atlantic corridor. NATS describes it as the first oceanic-airspace-scale trial focused on contrail avoidance.
The work will examine whether flight paths can be adjusted through small changes in cruising altitude to reduce the warming effect of persistent contrails. Contrails are condensation trails created by aircraft, and persistent examples can have a warming effect on the climate.
Two operational trials are planned for winter 2026-27 and winter 2027-28, with around 20 to 40 test days planned in each period. The winter testing has been selected because the project says contrail warming is particularly concentrated at that time of year.
Rather than making major route diversions, the trials will test relatively small changes in cruising altitude. NATS says the adjustments will be managed through normal air-traffic-control communication channels and are intended to take place during lower-traffic periods.
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NATS will lead the operational airspace activity, ATC coordination, safety assessment and controller training. The programme will assess both the environmental benefit and whether the approach is practical to operate, rather than assuming altitude changes could be introduced routinely.
The consortium also includes Google, the Department for Transport, the Met Office, Contrails.org, Imperial College London and the University of Cambridge. The Department for Transport is contributing £2.65 million through the Aerospace Technology Institute programme.
Google UK is providing £1.4 million in-kind through AI expertise, engineering time and high-performance computing resources. It will develop prediction tools using machine learning and satellite imagery to help assess the results of the trials.
The Met Office is developing a UK contrail-forecasting capability for the project, while Imperial College London and the University of Cambridge will independently evaluate the trial outcomes and climate effects.
NATS modelling indicates that Shanwick airspace represents about 5% of global contrail warming. The programme is a research and operational evaluation project and does not introduce a permanent change to North Atlantic flight levels or new passenger advice.
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