Designed for use as a military scout during the Vietnam War, the diminutive Hughes OH-6 Cayuse was the original winner of the LOH (Light Observation Helicopter) requirement for scout duties. It was small, extremely maneuverable, and instantly recognizable thanks to its small rounded fuselage. It was also commonly known as the 'Loach' due to phonetic similarites with the LOH acronym. During the Vietnam War, OH-6 helicopters were frequently teamed up with AH-1 gunships (a combination known as "Pink Teams") where they would scout for targets to be engaged by the Cobras. But despite its frailty, the Cayuse was eventually fitted with a wide array of armament including Hellfire and Stinger missiles, making it a potent attack platform in its own right. OH-6s adopted by around 30 countries including license production in Japan by Kawaski although it is now being replaced in the service by the newer OH-58.

Maiden flight of the YHO-6A (later YOH-6A) prototype was on 27 February 1963. It entered service as the OH-6A basic observation helicopter and immediately saw action in Vietnam. The OH-6A was eventually developed for a number of other roles such as the EH-6B command, control, and radio relay platform, the MH-6B for special operations, and the AH-6C light attack helicopter which was eventually nicknamed 'Little Bird'. These were subsequently improved as the AH-6J with more powerful engines, improved avionics including FLIR and can carry weaponry such as miniguns, rockets, anti-tank and anti-air missiles (a special operations version is the MH-6J). Other variants include the TH-6B Navy pilot trainer and the A/MH-6X unmanned air vehicles.