The Lockheed F-104 Starfighter was a single-engine, high-performance, supersonic interceptor aircraft that served with the United States Air Force (USAF) from 1958 until 1967. It continued in service with the Air National Guard until it was phased out in 1975. Subsequently, the National Aeronautics and Space Administration (NASA) continued to fly a small fleet. NASA F-104s flew in support of the X-15 and XB-70 projects. F-104s continued supporting the spaceflight programs until they were retired in 1995 and replaced by F/A-18 Hornets.