Secret aircraft of the USAF:

After years of secret development and testing, the Air Force recently declassified the TACIT BLUE program: the pathfinder project for today's stealth aircraft. Running from 1978-1985, the program provided a flight test platform to validate radar cross section reductions with curved surfaces and low probability of intercept radar techniques. At a final cost of $165 million, the TACIT BLUE program is now being declassified since the technology it evaluated is a part of the active inventory and the existence of the program no longer needs protection. On 22 May 1996, the only flight-worthy airframe used in the program was unveiled at the U.S. Air Force Museum, Wright-Patterson AFB, Ohio, where it is now on permanent display.