AI-Driven Route Planning Reduces Climate-Warming Contrails on Over 100 Flights

A comprehensive study examining thousands of flights between the United States and Europe revealed that contrails—those vapor trails left by aircraft—are less likely to form when planes follow artificial intelligence (AI)-recommended flight paths aimed at minimizing their global warming impact.

Contrails, created from soot particles emitted by aircraft engines, are believed to contribute significantly to warming, potentially surpassing the effects of carbon dioxide alone. Recent research indicates that certain icy areas in the upper atmosphere are more prone to contrail formation, and AI technology can predict these zones using detailed weather forecasts.

Despite the promising results from small-scale trials where aircraft avoid these high-contrail areas, such practices have not yet been widely implemented in commercial aviation.

In the study, Dinesh Sanekom and colleagues from Google utilized an AI-controlled contrail prediction tool to advise on flight routes in a randomized controlled trial involving over 2,400 flights with American Airlines.

This trial included overnight flights from the U.S. to Europe and spanned approximately 17 weeks, from January to May 2025. These flights specifically targeted nighttime, as contrails have an intensified warming effect during these hours due to reduced sunlight that reflects back into space during the day.

Flight routes between certain city pairs were randomly divided into two groups. The first group had the option to select an AI-optimized route that would result in fewer contrails, while the second group received no alternative route suggestions.

Although dispatchers were offered the opportunity to choose contrail-minimizing routes within the first group, only 112 of the 1,232 flights opted for these alternatives, primarily due to operational considerations such as cost and safety, Sanecom noted.

Analysis using satellite imagery of the flight paths indicated that flights adhering to AI-suggested contrail-optimized routes experienced a remarkable 62% reduction in visible contrails. When considering all flights that could have chosen these optimized routes, the overall decrease in contrail formation reached 11.6% compared to the control group.

“This supports our hypothesis that there is a scalable approach to implementing contrail avoidance across numerous flights if we can integrate it effectively and safely into flight planning,” Sanecom asserts.

Researchers calculate the global warming impact of air travel was diminished by 13.7% for the entire group utilizing the suggested routes, while flights using the optimized routes saw a substantial 69.3% decrease. Notably, no significant variations in fuel consumption were recorded between the groups.

“This approach is currently the most effective with the tools available,” states Edward Griespeerdt from Imperial College London. “The observed 62% reduction in contrails is unlikely to have occurred by chance.”

However, due to the intricacies of flight planning, it’s uncertain how much the 11.6% reduction could be realized in actual commercial operations, he added. “Scaling this to achieve a 60% reduction in contrails on every flight isn’t straightforward, but even a 10% reduction could yield a meaningful impact.”