High Quality Content by WIKIPEDIA articles! The Lockheed XV-4 Hummingbird (originally designated VZ-10) was a U.S. Army project designed and built by the Lockheed Corporation in the 1960s, one of many attempts to produce a V/STOL vertical take off/landing jet. At a design speed of 336 mph (541 km/h), the Hummingbird was slower than some propeller-powered transports. Both prototype aircraft were destroyed in accidents.