On 12 July 2010, in St Louis, Missouri, the Boeing Company unveiled the newest hydrogen powered spy-plane prototype, the Phantom Eye. Designed for advanced intelligence and reconnaissance missions, it is a high altitude, long endurance (HALE) unmanned aerial vehicle that will stay airborne for up to four days at altitudes of around 65,000 feet (19,800 metres). Its first flight is planned for the spring of 2011 at NASA’s Dryden Research Center, Edwards Air Force Base, California. The Phantom Eye ha a wingspan of 45.7 metres (150 feet), carries up to 205 kg (450 pounds) and is powered by two 2.3 litre four cylinder engines each producing 150 horsepower (111kW). The hydrogen propulsion system is efficient and the only by-product is water, so its production version will be a very green addition to the UAV reconnaissance fleet.