Fuel cell systems are regarded as a promising solution for future electrical energy generation on board of commercial aircraft. In addition to an improved efficiency such systems offer the opportunity of producing water usable for on-board purposes and provide additional functions such as inerting (providing a non-inflammable atmosphere) of the jet fuel tank. This paper presents an evaluation and assessment of different system architectures as well as experimental results demonstrating the feasibility of the multiple functions in a laboratory set-up. First, the conventional system requirements and the results reported by the Federal Aviation Administration (FAA) are discussed. A system design evaluation based on simulating cruise and ground operation of aircraft is performed demonstrating the benefits of systems with pressurized hydrogen tank storage and cabin air use. The requirements for a fuel cell system regarding aircraft inerting function are calculated based on the FAA analysis. Experimental results based on laboratory systems confirm the feasibility of the implementation of various functions with a single fuel cell system. Test platforms for further investigation of the systems are shortly described