There are two possible options for energy storages in future aircraft: batteries and hydrogen. In case of the use of a fuel cell, both require an electric drive system that generates the necessary thrust. Some key qualities in the design of such an electric drive system are reliability and fail-safe operation. Further, the choice of a drive system contributes to the overall aircraft weight not only with its own weight, but also by influencing the necessary energy to be stored due to different efficiencies for a given flight mission. Therefore, different options for drive systems have to be considered and evaluated regarding the following three key criteria: energy efficiency, power density and reliability.