1) Global Observer An aircraft that runs on liquid hydrogen has successfully conducted its first test flights by the U.S. company AeroVironment. It combines liquid hydrogen stored on board, pulled from the air with oxygen in fuel cells, and the propeller powered by electricity generated through this process. According to the company Aero vironment, the Global Observer aircraft can operate at 20,000 m in height by more than a week with a payload capacity of liquid hydrogen up to 0.45 Kg flexible The aircraft, called Global Observer and operates without a pilot. There is a row of eight propellers on the wing which are fed with hydrogen. The fact that the plane carrying liquid hydrogen on board means that it is imperative to isolate the tank where this is stored.The company has not released details about the design of the tank and not on the nature of the fuel cells that combine hydrogen and one part oxygen to one that draws from the sky while flying, but with this plane, using only two computers can rotate once a week each, without affecting the perfect communication and transmission of the same ground. AeroVironment plans to market aircraft such as Global Monitor as an alternative telecommunications platforms rather than existing satellites. In addition, aircraft which use hydrogen as an energy source would reduce the impact of aviation on climate change and greenhouse gas emissions that flights are growing faster than emissions from other sectors. New breakthroughs in clean fuels such as hydrogen, could help reverse this trend.