The Hughes OH-6 Cayuse is a single-engine light helicopter designed and produced by the American aerospace company Hughes Helicopters. Its formal name is derived from the Cayuse people, while its "Loach" nickname is derived from Light Observation Helicopter (LOH) program under which it was procured. The OH-6 was developed to meet United States Army Technical Specification 153, issued in 1960 to replace its Bell H-13 Sioux fleet. The Model 369 submitted by Hughes competed against two other finalists, Fairchild-Hiller and Bell, for a production contract. On 27 February 1963, the first prototype conducted its maiden flight. The Model 369 had a distinctive teardrop-shaped fuselage that was crashworthy and provided excellent external visibility. Its four-bladed full-articulated main rotor made it particularly agile, and it was suitable for personnel transport, escort and attack missions, and observation. During May 1965, the U.S. Army awarded a production contract to Hughes. During 1966, the OH-6 began service with the U.S. Army, and promptly entered active combat in the Vietnam War. In theater, it was commonly operated in teams with rotorcraft such as the Bell AH-1 Cobra attack helicopter, using so-called "hunter-killer" tactics to flush out and eliminate hostile ground targets. The OH-6 would act as bait to draw enemy fire and mark targets for other platforms such as the AH-1 to attack. In one clandestine incident in 1972, known as the Vinh wiretap, a pair of OH-6As were heavily modified and used by the Central Intelligence Agency (CIA) via Air America to infiltrate Vietnamese high level communications, providing valuable intelligence. Reportedly, 964 out of the 1,422 OH-6As produced for the U.S. Army were destroyed in Vietnam alone.[citation needed] During 1967, following price escalations for the OH-6, the U.S. Army reopened the program to bids for as many as 2,700 additional airframes beyond the 1,300 OH-6s already contracted. Following a competitive fly-off and a sealed bidding process, Hughes lost the contract to Bell, resulting in the competing Bell OH-58 Kiowa being produced. The OH-6/Model 369 was license-produced overseas by the Japanese aerospace company Kawasaki Heavy Industries for both military and civilian operators. It was also developed into a civilian helicopter, the Model 500, produced into the 21st century by MD Helicopters as the MD 500.[citation needed]