On July 7 of this year the Antares DLR-H2 motor glider became the first piloted aircraft to fly powered only by a fuel cell. The DLR-H2 has a fuel cell and hydrogen tank in underwing pods which powered an electric motor and propeller. Flying for the first time in Hamburg, Germany, the DLR-H2 has a range of 466 miles and a maximum speed of 106 mph with no emissions other than water vapor. The fuel cell delivers 20 kW of power and only 10 kW is needed to maintain level cruise flight. Total efficiency of the system is 44%- approximately twice the efficiency of a conventional piston engine.
Source: Aviation Week & Space Technology, July 13, 2009. "Industry Outlook" edited by Edward H. Phillips, p14.