The E-Fan X is a complex hybrid-electric aircraft demonstrator. In the test aircraft, one of the four jet engines will be replaced by a 2MW electric motor, which is roughly equivalent to that of 10 medium-sized cars. The electric propulsion unit is powered by a power-generation system and battery. When high power is required—at take-off, for example—the generator and battery supply energy together. If the aviation industry is to achieve its goal of a 50% reduction in net aviation CO2 emissions by 2050, future technologies in alternative propulsion must be accelerated. Our goal is to mature the technology, performance, safety and reliability, thereby accelerating progress on alternative propulsion. We also aim to establish the requirements for future certification of electric-powered commercial aircraft.