The plane was (sort of) a two-seat Dimona motor-glider with a 53.5 wingspan. It was modified by engineers belonging to Boeing's semi-legendary Phantom Works division so that it uses a hybrid system--with a Proton Exchange Membrane--that links an electric motor to a normal propeller. Its only waste products, as a result, are heat and water. Apparently the plane climbed to 3,300 feet on a mix of battery and fuel-cell power. Once at the specified cruising altitude, the pilot disconnected the batteries, and cruised for 20 minutes at 62 miles per hour with only the fuel cells to power the craft.