The Lockheed NF-104A was an American mixed power, high-performance, supersonic aerospace trainer that served as a low-cost astronaut training vehicle for the North American X-15 and projected Boeing X-20 Dyna-Soar programs.
Three aircraft were modified from existing Lockheed F-104A airframes, and served with the Aerospace Research Pilots Schoolbetween 1963 and 1971, the modifications included a small supplementary rocket engine and a reaction control system for flight in the upper atmosphere. During the test program, the maximum altitude reached was more than 120,000 feet (36,600 m). One of the aircraft was destroyed in an accident while being flown by Chuck Yeager. The accident was depicted in the book The Right Stuff and the film of the same name.