An American Airlines plane flying in against a clear blue sky

Contrail avoidance

American is helping lead the way toward developing and testing contrail avoidance methods. Contrails—or condensation trails — form when airplanes fly through layers of humidity, and they may account for approximately 35% of aviation’s global warming impact, according to the IPCC. Contrail avoidance strategies, while still in the early stages of exploration, hold the promise of being among the most cost-effective and scalable decarbonization solutions available in the near term.

Diagram showing contrails and their effect on warming — Contrails form when a plane's hot, humid exhaust mixes with cool, humid air high in the atmosphere and creates ice. Contrails are similar to naturally occurring cirrus clouds — and they affect the climate in the same way. But aviation artificially increases the amount of cirrus clouds in the atmosphere. During the day, contrails reflect some sunlight back into space, and therefore have a weak cooling effect. At night, contrails exclusively trap heat, meaning they have a strong warming effect that more than offsets the weak daytime cooling effect. Persistent nighttime contrails — meaning those that don't dissipate quickly — have the most warming impact. Avoiding these is the highest-value intervention.

Teaming up with Google Research and Breakthrough Energy

In 2023, American participated in a first-of-its kind study led by Google Research (opens in new tab) and Breakthrough Energy (opens in new tab) to help advance the science on contrail avoidance. The study tested whether we could identify atmospheric zones likely to create contrails so that pilots could avoid creating them when provided with this data. Our partners combined large data sets — including satellite imagery, weather and flight path data — with artificial intelligence (AI) to develop contrail forecast maps. A small group of American pilots then flew 70 flights over six months, using the AI-based predictions to make small modifications to routes that were projected to create contrails.

The flights that used the AI predictions reduced contrail formation by 54%, as measured by distance, compared to flights where pilots did not use the predictions. While additional research is needed to determine if this success can be replicated and scaled, the results of this small-scale test provide an encouraging proof point of a promising climate solution.

Contrail avoidance

Teaming up with Google Research and Breakthrough Energy

54% drop in contrail formation on our test flights that used AI predictions

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