The main objective of the FlyATM4E project is to expand approved climate-assessment methods and optimization of aircraft trajectories in order to identify promising mitigation options suitable to solve the task of reducing overall climate impact of aircraft operations. FlyATM4E will develop a concept to identify climate-optimised aircraft trajectories which enable a robust and eco-efficient reduction in aviation’s climate impact. FlyATM4E will identify those weather situations and aircraft trajectories, which lead to a robust climate impact reduction despite uncertainties in atmospheric science that can be characterised by ensemble probabilistic forecasts.