American Airlines and Google say AI helped airplanes reduce contrails that trap heat

American Airlines and Google said Thursday they have significantly reduced the climate impact of some of the airline’s flights by using an AI-based forecasting tool to help prevent contrails.

When planes fly through cold, wet areas, ice crystals can form around soot particles emitted by the engine, creating clouds that trap heat and warm the planet. Google uses artificial intelligence to predict where these contrails, or contrails, are likely to form if planes pass by. American Airlines added the forecast to its flight planning system on a trial basis to show where pilots could safely change altitude or use optional routes to avoid those areas.

American Airlines and Google said the tool could be one of the most cost-effective and scalable climate solutions currently available in the aviation sector.

The aviation industry is under increasing pressure to act on climate change. And while those thin white lines that form behind planes may look wispy, they’re responsible for a surprising amount of Earth’s warming: 1 to 2 percent, according to Contrails.org, a nonprofit research organization dedicated to reducing the climate impact of aviation through contrail management, as part of the Breakthrough Energy group founded by Bill Gates. The group was among the collaborators in the trial.

Switching to cleaner fuels, such as sustainable aviation fuel, can significantly reduce emissions and contrails, although it costs much more than slightly changing a flight route.

Many contrails are short-lived, but some can persist for hours or even days if the weather is extremely humid. Research on the subject suggests that minor adjustments to flight altitudes or routes to avoid these regions could eliminate a significant portion of this warming using a minimal amount of additional fuel – a theory tested in this trial.

The trial involved 2,400 flights from the United States to Europe. In research shared in a blog post Thursday, Google said half of the participants were given a route option to avoid creating contrails and the other half made up the control group.

For the 112 flights that used this option, they formed 62% fewer contrails compared to the control group, the paper said. Researchers estimated that this reduced climate warming from these flights by about 69%.

The trial began in January 2025 and ended in May. Flightkeys, the flight planning service used by American Airlines, has joined the airline, Google and Contrails.org in the collaborative work.

“We know that aviation is one of the hardest sectors to decarbonize,” Dinesh Sanekommu, who leads Google’s work on contrails, said in an interview. “We think there’s a way that AI can help make this a reality. And the hope is that whether it’s these AI-based predictions or these operational science demonstrations done together, they all add a little bit of evidence and generate a little bit of data that helps make the right decisions in the long term.”

This builds on previous work from Google, American Airlines and Breakthrough Energy. They teamed up in 2023 to reduce the warming effects of contrails and conducted a smaller test in which flights were identified manually rather than integrated into the flight planning system.

As for what’s next, Sanekommu said they need to do a broader trial and want to work with all other flight planning software vendors to incorporate contrail forecasts and avoidance features into their products.

One of the main deterrents preventing airlines from adjusting a route is the potential cost of additional fuel, but the trial found no statistically significant difference in fuel consumption observed between the two groups.

Coordination between pilots and air traffic controllers in different regions of international airspace is also a challenge, said Thomas Walker, who studies the climate impacts of aviation at the Boston-based Clean Air Task Force. The CATF has talked with other major airlines about avoiding contrails, Walker said, and “there’s been a bit of pushback.”

Jill Blickstein, vice president of sustainability at American Airlines, said the trial showed it was not difficult for regulators and pilots to file and pilot alternative plans to avoid contrails.

The North Atlantic region is a hot spot for contrails, making attempts to avoid their creation there particularly effective, added Walker, CATF’s senior director of transportation technology.

Walker said there have been trials in Europe to adjust routes, and this is the largest he’s heard of in the United States, which is “a pretty big step in the right direction.” He said he hoped American Airlines’ positive results would encourage other airlines to participate.

American Airlines said it has not yet incorporated contrail prevention into its regular flight planning process. The airline said it hopes to continue working with its partners on additional studies, potentially involving different flight routes and times of day, that could help answer important scientific questions.

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