A small change in cruising altitude could take a meaningful slice out of aviation’s climate footprint, if early findings from the Cathay Pacific contrail avoidance trial with Google hold up as the work grows.
The partnership makes Cathay Pacific the first airline in Asia-Pacific to test Google’s AI-powered system, and the first anywhere to try it on ultra-long-haul flights. For UK businesses sending staff to Hong Kong, Singapore and beyond, it is a sign that airlines are looking past fuel alone to reduce the climate impact of long-haul trips.
Are contrails bad for the environment?
They can be. Contrails, short for condensation trails, are the white streaks aircraft leave behind when they cruise through cold, moist air far above the ground. Some persist and spread into layers of cloud that hold heat in the atmosphere.
Aircraft contrails that linger in this way could potentially account for around one-third of aviation’s total climate impact. That warming effect is separate from the carbon dioxide released when jet fuel is burned, which is why steering clear of the conditions that create them has drawn growing interest from researchers and airlines.
How the Cathay Pacific contrail avoidance trial works
Google’s system uses AI prediction models, satellite images and weather data to forecast where contrails are likely to form. It then gives pilots live advice on the altitude changes needed to avoid those zones. The guidance appears directly in Cathay Pacific’s Electronic Flight Folder, reaching the flight deck through the aircraft’s onboard connectivity.
Flights testing the approach are already operating across the Hong Kong-based airline’s global network. Early results from more than 80 flights that followed contrail avoidance guidance show an estimated 40 per cent reduction in warming impact, according to Cathay Pacific’s announcement of the Google partnership.
One route stood out. The Hong Kong-Singapore corridor delivered more than half of the trial’s total climate benefit, and it did so through minor altitude changes alone.
The two companies are now moving into a larger second phase spanning Asia and transpacific routes. The aim is to build a wider body of data that can inform best practice and policy for the whole industry.
What it means for business travel emissions
Efforts to cut business travel emissions have so far leaned heavily on sustainable aviation fuel. Google has taken that route itself, having extended its sustainable aviation fuel deal with Amex GBT and Shell earlier this year. Supply remains tight, however, as our analysis of the SAF slowdown and what it means for business travel sets out.
Contrail avoidance tackles a different part of the problem. If the Cathay Pacific contrail avoidance results are repeated at scale, the climate effect of a long-haul trip could come to depend not only on the aircraft and its fuel, but on how it is flown on the day.
The idea is also being tested closer to home. Google is part of Operation Blue Skies, a £5 million, 30-month programme partly funded by the UK Department for Transport, which will trial contrail avoidance in NATS-controlled Shanwick oceanic airspace over the eastern North Atlantic during the winters of 2026-27 and 2027-28. That is the corridor used by many of the flights UK business travellers take to North America.
For travel managers, there is nothing to book or pay for yet, and the figures so far are estimates from a limited trial. Even so, companies with sustainability targets for travel may want to ask airline partners what they are doing about contrails, alongside fuel and fleet plans, when contracts come up for review. Those balancing cost against climate goals will find practical pointers in our expert advice on navigating the cost of going green.
