The Boeing X-45 Spiral is an UCAV it´s a demonstrator aircraft for the next generation of autonomous combat aircraft developed by Phantom Works, it was a part of DARPA´s and J-UCAS (Joint Unmanned Combat Air systems) program.
After termination it was evolved by Boeing into the Boeing Phantom Ray.
The Boeing X-45 was developed from the results of the Phantom Ray program. The X-45 has a unusual flat engine inlet, which is close to the leading edge. The exhaust outlets are close to the lambda wings. The X-45 is not equipped with vertical stabilizators; the splitted ailerons on the wingtips act as an asymmetrical air brake, which are used as rudders.
Boeing built two subscale X-45A, to show, that the concept will be successful. The larger X-45B was later modified into the X-45C and was equipped with larger fuel tanks (range was increased to 1,930 km). The leading edge of the wings is spanned from the wingtip up to the nose of the aircraft, similar like on the Northrop B-2 Spirit. The X-45C was completed in 2006 and capability demonstration started in 2007. The first aerial refueling by a KC-135 was in 2010. A mock-up of a X-45N designed for naval service was unveiled at the Farnborough International Air Show 2006.
In October 2004 the X-45C project received 767 milion US-Dollar by DARPA, to built and test three aircraft. In July 2005 the project received again money (about 175 milion US-Dollar), to continue the project and to develop autonomous aerial refueling. On 2nd March 2006, the United States Air Force decided to cancel the X-45C project. After that, Boeing tried to modify the X-45C for the needs for the United States Navy.