With the increasing concerns about environmental pollution, several international organizations are setting more restricting rules for aircrafts homologation, similarly to what is happening in the Automotive field. The CO2 produced by the global aviation constitutes about the 2% of the total related to humans activity. Even if this percentage seems not much relevant, each year more than 900 million metric tons of carbon dioxide are emitted by the aviation industry, with an increasing trend that raises many concerns about the global warming. At the aircraft level, the only way to reduce as much as possible the CO2 emissions is the adoption of electric solution, based on batteries or hydrogen as main energy source.