The first flight of the turboshaft-powered S-64 Skycrane was 9 May 1962, with the United States Army eventually purchasing 105, designating them CH-54. Used in Vietnam for transport and downed-aircraft retrieval, it was highly successful, thanks to the 'adaptable' nature of the module system first conceived by General James M. Gavin in his book Airborne Warfare in 1947. Early pods could not carry troops and external sling-loads at the same time. Advanced pods for the CH-54 could carry troops and cargo underslung at the same time but were not purchased. The Skycrane can not only hold its cargo up and tight against its center spine to lessen drag and eliminate the pendulum effect when flying forward, it can winch vehicles up and down from a hovering position, so the helicopter does not need to land. Due to budget cuts the Heavy Lift Helicopter (HLH) program was canceled and the CH-54s not upgraded with larger engines. The BoeingCH-47 Chinook gradually supplemented it in combat and eventually replaced it in Regular Army aviation units, although CH-54 Skycranes remained in Army National Guard service until the early 1990s. The Soviet Union also created much larger crane helicopters with a similar skeletal design.
Today, Erickson Air-Crane of Central Point, Oregon operates the largest fleet of S-64 helicopters in the world under the name Erickson S-64 Aircrane, which can be equipped with water-dropping equipment (some also have foam/gel capability) for firefighting duties worldwide. After obtaining the type certificate and manufacturing rights in 1992, Erickson remains the manufacturer and world's largest operator of S-64s.