The manuscript presents the conceptual design phase of an unmanned aerial vehicle, withthe objective of a systems approach towards the integration of a hydrogen fuel-cell system and Li-ionbatteries into an aerodynamically efficient platform representative of future aircraft configurations.Using a classical approach to aircraft design and a combination of low- and high-resolution computationalsimulations, a final blended wing body UAV was designed with a maximum take-off weightof 25 kg and 4 m wingspan. Preliminary aerodynamic and propulsion sizing demonstrated that theaircraft is capable of completing a 2 h long mission powered by a 650Wfuel cell, hybridized with a100 Wh battery pack, and with a fuel quantity of 80 g of compressed hydrogen.