In order to meet the increasing pressure to reduce fuel consumption and greenhouse gas emissions, airlines are seeking alternative sources to power non-propulsive aircraft systems. The next generation of aircraft is heavily investigating the use of non-fossil fuel to generate electrical power for non-essential applications (NEA). Hydrogen fuel cells are actively being pursued as the most promising means of providing this power. Fuel cells also have the added benefits of no pollution, better efficiency than conventional systems, silent operating mode and low maintenance. The by-products from the fuel cells (heat, water and oxygen depleted air) will also have a positive impact on the global aircraft efficiency when they are harnessed and reused within the aircraft system.The HYCARUS project will design a generic PEM fuel cell system compatible of two NEA, then develop, test and demonstrate it against TRL6. A secondary electrical power generation model for a business executive jet will be run. The application will be tested with the fuel cell system and the storage system under flying conditions. Furthermore, investigations will be made to understand how to capture and reuse the by-products.The HYCARUS project will extend the work already completed in the automotive sector, particularly for safety codes and standards, and develop these for use in airborne installation and applications. Improvements in terms of efficiency, reliability, performance, weight /volume ratio, safety, cost and lifetime under flight conditions at altitude and under low ambient temperatures (mainly in the air) will also be examined.The HYCARUS project also aims to foster a better and stronger cooperation between all the agents of the sector: Aeronautics equipment and systems manufacturers, aircraft manufacturers, system integrators and fuel cell technology suppliers.