Flying alternative trajectories for the benefit of Climate F4ECLIM's primary aim is to advance aCCFs by integrating weather forecasts and climate science to address uncertainties tied to CO2, contrails, ozone, methane, and water vapor climate effects. This involves evolving aCCFs to version 2.0, broadening their geographical scope (currently limited to the North Atlantic), considering diverse weather and seasonal patterns, and incorporating various climate metrics. These advancements will feed into a climate service for the aviation community. Additionally, F4ECLIM will explore aviation's potential to reduce its climate impact through the development of robust flight planning algorithms. These algorithms will identify eco-efficient aircraft trajectories, assessing the associated climate impact reduction and costs. Backtesting procedures will be employed to scrutinize trajectories and climate models, providing insights into model specifications. The project will culminate in recommendations and the introduction of key performance indicators (KPIs) to guide stakeholders in implementing eco-efficient trajectories, reducing uncertainties, and advancing understanding of the non-CO2 impact of aviation for a greener future.