Google Research, American Airlines and Bill Gates’s Breakthrough Energy have used artificial intelligence (AI) to develop contrail forecast maps that reduced the contrails of test flights by 54%. The technology holds the potential to vastly reduce the detrimental climate impact of flying.

Contrails – the thin, white lines produced by airplanes in the sky – account for roughly 35% of aviation's global warming impact, more than half the impact of the world’s jet fuel, according to a 2022 Intergovernmental Panel on Climate Change report. They form when planes fly through layers of humidity and they can persist as cirrus clouds, sometimes for hours, trapping large amounts of heat in the Earth’s atmosphere. Avoiding flying through areas that create contrails can reduce warming, so the challenge is identifying which flight routes will create contrails.

Over six months, American Airlines pilots flew 70 test flights using Google’s AI-based predictions, cross-referenced with Breakthrough Energy’s open-source contrail models, to avoid altitudes likely to create contrails. Google Research subsequently analysed satellite imagery and found the pilots were able to reduce contrails by 54%, proving for the first time that commercial flights can verifiably avoid contrails and thereby reduce their climate impact.

The research also found that the flights that attempted to avoid creating contrails burned 2% more fuel. Recent studies indicate that only a small percentage of flights would have to be altered to avoid the majority of contrail warming. This means that the total fuel impact could be as low as 0.3% across an airline’s flights, suggesting that contrails could be avoided at scale for around $5–25/tonne CO₂e (carbon dioxide equivalent) using Google’s existing predictions. These savings would already make it a cost-effective warming-reduction measure, but further improvements are expected as the research continues in the coming years.