The Northrop T-38 Talon is an American supersonic jet trainer. It was the world s first and most produced supersonic trainer. It remains in service as of 2009 in air forces throughout the world including the United States Air Force (USAF) which remains its largest user. The basic airframe was used for the light combat aircraft F-5 Freedom Fighter family. In addition to USAF pilots T-38s are also used by NASA astronauts the U.S. Naval Test Pilot School (other T-38s were previously used as USN aggressor aircraft) other NATO pilots under a joint training program and some under civilian ownership.