This aircraft is the first X-35 ever built. It was originally the X-35A and was modified to include the lift-fan engine for testing of the STOVL concept. Among its many test records, this aircraft was the first in history to achieve a short takeoff, level supersonic dash, and vertical landing in a single flight. It is also the first aircraft to fly using a shaft-driven lift-fan propulsion system. The X-35B flight test program was one of the shortest, most effective in history, lasting from June 23, 2001 to August 6, 2001.The lift-fan propulsion system is now displayed next to the X-35B at the Steven F. Udvar-Hazy Center near Dulles Airport.On July 7, 2006, the production model F-35 was officially named F-35 Lightning II by T. Michael Moseley, Chief of Staff USAF.