Proposals were submitted by Bell, Boeing Vertol/Grumman team, Hughes, Lockheed, and Sikorsky. In July 1973, the U.S. Department of Defense selected finalists Bell and Hughes Aircraft's Toolco Aircraft Division (later Hughes Helicopters). This began the phase 1 of the competition. Each company built prototype helicopters and went through a flight test program. Hughes' "Model 77/YAH-64A" prototype first flew on 30 September 1975, while Bell's Model 409/YAH-63A prototype first flew on 1 October 1975. After evaluating the test results, the Army selected Hughes' YAH-64A over Bell's YAH-63A in 1976. Reasons for selecting the YAH-64A included its more damage tolerant four-blade main rotor and the instability of the YAH-63's tricycle landing gear arrangement.