Operation Blue Skies consortium to carry out testing in Shanwick oceanic airspace from later this year.
Operational evalutions are set to begin later this year of an airspace-scale contrail avoidance trial through a 30-month project part-funded by the UK government.
To take place in Shanwick oceanic airspace, the eastern half of the North Atlantic corridor, the tests are designed to evaluate the feasibility of adjusting the altitude of flights to avoid the thin band of the atmosphere in which contrail creation can occur.
Unlike previous trials, it will be the first that seeks to redirect all flights within a block of airspace, rather than simply those from a single carrier.
Called Operation Blue Skies, the tests will be delivered by a consortium that includes Google, the UK’s Department for Transport (DfT), the Met Office, air navigation service provider NATS, non-profit research group Contrails.org, Imperial College London, and the University of Cambridge.
Using AI-backed models produced by Google – which is contributing to the project on a pro bono basis – the consortium will be able to identify areas of ice super-saturated air in which persistent contrails are formed and reroute flights to avoid them.
While these areas tend to extend over a wide horizontal area, they are typically only found in a narrow band between 36,000-40,000ft, allowing them to be avoided by relatively minor changes in altitude.
In fact, the deviations to be proposed by NATS controllers will be limited to around 2,000ft, says Dr Paul Hodgson, Google technical lead for Operation Blue Skies, limiting fuel-burn increases to around 1%, or around 100kg, for the Shanwick portion of the flight.
Comparatively, the equivalent impact of contrails “is measured in tons or even tens of tons”, he adds. “So the ratio of contrail impact to CO2 impact is at least an order of magnitude, if not orders of magnitude.”
Additionally, with all traffic subject to the trial, pilots will not be given the choice of opting in or out of the flight-level changes, which will be delivered as part of normal control procedures.
“The air traffic controllers will deal with ice super-saturated regions where they are, and if it’s possible, if it’s safe and operationally feasible to move the aircraft to avoid the regions, then they will do that,” says Ian Jopson, sustainability director at NATS.
“It’s just a standard procedure, but just one we are putting in place for contrails rather than other things like turbulence or other sorts of weather.”
Such an approach will also minimise the additional workload imposed on controllers, Jopson notes.
Trials will be conducted in the evenings and nights over two winter testing windows in 2026-2027 and 2027-2028, with around 20-40 test days – effectively a 7-8h block – in each November to February period. Other days will serve as control periods for the overall project.
These periods have the advantage of being quieter and also most prone to contrail persistence, says Hodgson.
Although individual airlines were also excluded from the consortium to avoid any accusations of bias, “nonetheless we have been doing a lot of engagement with the airlines and that is ongoing and will continue throughout”, he adds.
The UK government is providing £2.65 million ($3.6 million) to the project through the Aerospace Technology Institute (ATI), while Google’s contribution is valued at £1.6 million.
Although shorter-lived than CO2 emissions, persistent warming contrails are thought to contribute around one-third of aviation’s total climate impact.
Atmospheric modelling shows that the Shanwick airspace accounts for approximately 5% of global contrail warming.
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