Boeing–Sikorsky RAH-66 Comanche

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.