"In response to the stated requirements for a Utility Tactical Transport Aircraft System (UTTAS), the Sikorsky company and Boeing-Vertol entered a competition to produce a prototype to be selected for production. Sikorsky's Model S-70 became the YUH-60A, and Boeing-Vertol's Model 179 was designated the YUH-61A. In 1976 when the modifications, tests, and competition finished, the Army selected the Sikorsky aircraft. By 1978 the first UH-60A "Blackhawks" were delivered. "This example, one of the original YUH-60A prototypes, featured a fully articulated 4-blade main rotor, a fixed position undercarriage landing gear, and a cabin large enough for a 3-4 man crew and an 11-man infantry squad. Significant modifications as a result of early tests included raising the heights of the main rotor above the fuselage by some 15 inches and adopting an all-moving tail surface. "The Blackhawk is capable of being configured with a hover infrared suppressor sub-system, a mine delivery system, an electronic countermeasures kit, as well as being capable of loading up to 16 Hellfire missiles (with an additional 16 in the cabin for reloading). The Army Special Operations forces also have unique requirements that include additional external fuel storage, uprated engines, provisions for air-to-air refueling, a rescue hoist, and advanced avionics. "The UH-60 series has seen modifications that have allowed its usage by all branches of the armed forces. The UH-60 series has proven to be one of the most powerful and versatile aircraft in the Army inventory to date."