Equipped with an experimental fuel cell system to power the aircraft at night, the solar-electric Helios Prototype is shown during a checkout flight prior to its long-endurance flight demonstration June 7, 2003 ED03-0152-1 ED03-0152-1 NASA's Helios Prototype electrically powered flying wing began a checkout flight June 7 from the Navy's Pacific Missile Range Facility on the Hawaiian island of K..