The Boeing–Sikorsky RAH-66 Comanche is an American stealth armed reconnaissance and attack helicopter designed for the United States Army. Following decades of study and development, the RAH-66 program was cancelled in 2004 before mass production began, by which point nearly US$7 billion had been spent on the program. During the early 1980s, the U.S. Army started to formulate requirements for the replacement of its helicopters then in service, which resulted in the launch of the Light Helicopter Experimental (LHX) program. Nearly a decade later, following the refinement of requirements, evaluation of submissions, and the rebranding of the program as the Light Helicopter (LH) program, during April 1991, the Army announced the selection of the Boeing–Sikorsky team's design as the contest winner, shortly after which a contract for construction of prototypes was awarded. The Comanche was to incorporate several advanced elements, such as stealth technologies, and a number of previously untried design features. Operationally, it was to employ advanced sensors in its reconnaissance role, in which it was intended to designate targets for the AH-64 Apache. It was also armed with one rotary cannon and could carry missiles and rockets in internal bays and optionally on stub wings for light attack duties. Two RAH-66 prototypes were constructed and underwent flight testing between 1996 and 2004. On 1 June 2000, the program entered its $3.1 billion engineering and manufacturing development (EMD) phase. However, during 2002, the Comanche program underwent heavy restructuring; the number of Comanches that were to be purchased was cut to 650. At the time, the projected total cost for the full production of the Comanche in such numbers stood at $26.9 billion. As early as the late 1990s, the Government Accountability Office (GAO) had reported that it had "serious doubts" about the program, observing that the Comanche would "consume almost two thirds of the whole Aviation budget by Fiscal Year 2008". Multiple government agencies had acted to cut the number of Comanches on order, but, as a consequence of the heavy reductions to the numbers to be procured, the unit costs soared. On 23 February 2004, the U.S. Army announced the termination of the Comanche program, stating they had determined that the RAH-66 would require numerous upgrades to be viable on the battlefield and that the service would instead direct the bulk of its rotary systems funds to renovating its existing attack, utility, and reconnaissance helicopters. The Army also announced new plans to accelerate the development of unmanned aerial vehicles (UAVs), which could also perform the scouting role intended for the Comanche, but with less risk. Since program cancellation, both of the prototypes have been placed on public display.