Air France tested a new method to reduce the environmental impact of its flights between February and April 2026. The airline modified the routes of 130 transatlantic flights to avoid areas where aircraft are likely to create persistent condensation trails, also known as contrails. These trails form when water vapor from jet engines freezes in cold, humid air at high altitudes. When they persist and spread, they can act like artificial clouds, trapping heat and contributing to global warming. The experiment, conducted in collaboration with two French start-ups, Estuaire and Klima, was part of the European research program CICONIA. To identify areas with the highest risk of persistent contrail formation, Air France used weather forecasts, flight data, and specialized models. Based on this information, alternative routes were suggested to pilots and air traffic control. Out of nearly 4,300 flights analyzed, 245 were found to have a high potential climate impact due to contrails. Ultimately, 130 flights were rerouted to avoid these areas when possible. These flights connected France with North America, Mexico, and the Caribbean, and the changes in route were made without causing delays for passengers. According to Air France, the rerouted flights reduced the climate impact of contrails by 57% on the affected routes. When considering all climate factors, including the potential for increased fuel use from rerouting, the overall reduction in impact was estimated at 36%. Across all flights tested, the climate impact from contrails decreased by 8%, which the airline calculates as equivalent to avoiding 22,000 tonnes of CO2 emissions. The experiment is part of the CICONIA project, which includes major players in the aviation industry such as Airbus, Boeing, easyJet, and SWISS, as well as research institutions and meteorological services. The North Atlantic airspace was chosen for the test because it is less congested than other regions, making it easier to adjust flight paths. The next challenge is to apply this method in more crowded airspace, where rerouting options are more limited. While reducing contrails is not a substitute for other efforts to decarbonize aviation, such as using sustainable fuels or improving efficiency, it could serve as a useful addition to these strategies if weather forecasts are accurate and rerouting does not lead to excessive fuel use.