Cathay Pacific and Google are moving to a new stage in the use of artificial intelligence to reduce aviation’s climate impact. After an initial operational trial involving more than 80 flights, the partners are expanding tests designed to avoid persistent contrails. Google’s satellite analysis suggests that flights following avoidance routes cut the warming effect associated with those contrails by around 40%.
Small altitude changes instead of a new aircraft technology
The concept is operational rather than mechanical. Persistent contrails form when aircraft cross very cold and humid layers at high altitude. When those trails spread and linger, they can create artificial cloud cover that traps part of the Earth’s outgoing heat.
Google combines AI-based forecasts, meteorological data and satellite imagery to identify areas where persistent contrails are most likely to form. Flight planners and crews can then consider small altitude changes to avoid those zones, subject to the usual safety, fuel and air-traffic-control constraints.
More than 80 flights have already used avoidance trajectories
The first phase targeted more than 100 Cathay Pacific flights, and more than 80 of them actually used modified trajectories.
Google estimates, based on satellite observations, that those flights reduced the warming effect of the contrails they would otherwise have created by roughly 40%.
That figure needs context. It is an estimate generated by the technology partner, not an independent measurement of a 40% reduction in Cathay Pacific’s overall climate footprint.
The real significance is that contrail mitigation can potentially be applied to existing aircraft without waiting for an entirely new propulsion system.
Cathay Pacific is taking the experiment into ultra-long-haul operations
Cathay is Google’s first commercial airline partner in Asia-Pacific for this phase of the work and, according to the partners, the first airline to test contrail avoidance on ultra-long-haul services.
The Hong Kong–Singapore corridor formed part of the trial environment. The second phase is intended to expand testing across Asian and transpacific operations, with Contrails.org also participating.
That wider geography matters because weather, airspace structures, traffic density and cruise-level availability differ significantly between regions.
Forecasts can be transmitted all the way to the cockpit
The system is not limited to a pre-departure planning map.
Cathay can transmit updated contrail-risk information to the flight deck through onboard connectivity and its Electronic Flight Folder, allowing crews to see likely contrail-forming regions alongside normal operational information.
The principle is similar to altitude adjustments already used to avoid turbulence or adverse weather. The difference is that the environmental benefit must always be weighed against any extra fuel burn caused by a route or altitude change.
The climate issue goes beyond CO₂
Aviation decarbonisation is usually discussed in terms of newer aircraft, sustainable aviation fuel and future propulsion technologies.
Contrails highlight a different part of the climate equation: non-CO₂ effects.
Google estimates that persistent contrails could account for around one third of aviation’s total climate impact. That estimate remains the subject of scientific refinement, but it explains why the sector is increasingly interested in operational avoidance.
The attraction is obvious: unlike fleet replacement or hydrogen propulsion, contrail avoidance could potentially be deployed progressively with today’s aircraft.
The idea has already been tested with American Airlines
The Cathay programme builds on earlier Google work with American Airlines.
A previous trial involving around 2,400 transatlantic flights found a significant reduction in contrail formation on flights that followed the recommended avoidance trajectories.
Moving to Cathay Pacific allows the method to be tested in Asia-Pacific and on much longer missions, adding operational diversity that is essential before any large-scale deployment.
The key question: does the climate benefit exceed the fuel penalty?
Contrail avoidance is not automatically beneficial every time.
Changing altitude or route can increase fuel burn. If that increase is too large, part of the climate benefit can be lost.
The operational challenge is therefore to identify the small number of situations where a limited trajectory change avoids a high-impact persistent contrail at a low fuel cost.
Promising, but still under evaluation
The first results are encouraging, but this is not yet a universal operational standard.
Altitude changes remain subject to ATC clearance, aircraft performance, weather, traffic conflicts and available flight levels.
The second phase announced on September 7 is designed to study those trade-offs on a larger sample.
If the results continue to hold, predictive contrail avoidance could become one of the few near-term climate measures available to airlines without waiting for a new aircraft generation.
Main sources
Cathay Pacific, September 7, 2026; Google Research; Reuters; previous Google–American Airlines contrail-avoidance work.
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