Google Adjusts Over 100 Flights to Reduce Climate-Warming Contrails

A recent study involving thousands of flights between the United States and Europe indicates that contrails—a factor in global warming—are significantly reduced when aircraft follow AI-recommended flight paths.

These condensation trails, formed by soot particles from aircraft engines, are suspected to contribute more to global warming than the carbon dioxide emissions from airplanes. Additionally, research indicates that specific icy regions in the upper atmosphere are more prone to contrail formation, and AI can effectively utilize detailed weather forecasts to identify these areas.

Initial small-scale trials demonstrate that rerouting planes can diminish contrail formation, yet this method has not been extensively implemented for commercial flights.

In a collaborative study, Dinesh Sanekom and his team at Google employed an AI-based contrail prediction tool to optimize flight routes during a randomized controlled trial involving over 2,400 American Airlines flights.

This examination spanned approximately 17 weeks from January to May 2025 and included eastbound flights from the U.S. to Europe at night, when contrails are known to exert a stronger warming influence. During daylight, contrails tend to reflect solar radiation, thus generating a cooling effect.

Each flight path between two cities was randomly allocated to one of two groups. The first group had access to an AI-optimized route in their flight planning software, allowing them to select paths with fewer contrails; in contrast, the second group received no such suggestions.

Though dispatchers in the first group had the choice of selecting contrail-optimized routes, logistical concerns led only 112 out of 1,232 flights to opt for alternate paths, according to Sanecom.

AI analysis using satellite imagery revealed that flights utilizing contrail-optimized routes suggested by air traffic controllers experienced a 62% decrease in visible contrail formation. When considering all flights with access to contrail-optimized routes, the overall contrail reduction compared to the control group was 11.6%.

“These findings validate our hypothesis that scalable routes can effectively mitigate contrail formation on numerous flights, provided we safely and accurately integrate this process into flight planning,” says Sanecom.

Researchers estimated that the overall global warming impact of flights was reduced by 13.7% for the group utilizing the suggested routes, and by as much as 69.3% for flights that implemented the optimized routing. Notably, there was no significant difference in fuel consumption between the two groups.

“This approach may represent the most effective solution available today,” states Edward Grisspeed from Imperial College London. “The observed 62% reduction in contrails identified by satellite is unlikely to be coincidental.”

However, due to the intricacies of flight planning, the extent of the 11.6% reduction may not entirely reflect real-world operations, as Grisspeed notes: “It’s challenging to extrapolate this to achieve a 60% reduction in contrails for every flight. Even a 10% reduction, though, would create a meaningful impact.”