The increasing demand for global air travel has intensified the urgency to mitigate aviation’s carbon emissions. Continuous monitoring of aircraft fuel efficiency and emissions has become an important task in aviation. One of the main challenges has been the lack of surveillance data for flights across oceans, specifically in the North Atlantic region, where numerous flights occur. Recently, space-based ADS-B data has been made available by new space companies like Spire Global, enabling flight surveillance for aircraft in remote regions, including transatlantic flights. In this study, we utilize several months of space-based ADS-B data from Spire, combined with groundbased ADS-B data from the OpenSky Network, to demonstrate increased accuracy in flight trajectory and emission estimations. We introduce the use of wind data to improve emission quantification. Utilizing these accurate trajectories, we quantify excess emissions by comparing actual flight paths with their optimal alternatives. Our approach provides a robust methodology that benefits future policy for carbon emissions assessments. @en