In 1961, the US Air Force planned to procure a strategic long-range transport aircraft with a view to its aging C-124 and C-133 transporter fleet with propeller drive. Studies for a CX-4 project began in 1963, and in May 1964 Boeing, Douglas and Lockheed were commissioned to further develop their previous designs. General Electric and Pratt & Whitney were commissioned to develop new turbo fans. The selection was made in 1965: The Lockheed-Georgia Company received the order for the development and construction of the C-5 "Galaxy" (company name L-500), the General Electric Company was commissioned with the development and manufacture of the TF-39 engine.
Construction of the four-engine C-5 began in 1966, and on March 2, 1968, the first C-5 left the assembly shop. The aircraft made its maiden flight on June 30, 1968. The C-5 was the largest aircraft in the world at the time. It was only surpassed in 1982 by the Antonow An-124 and in 1988 by the Antonow An-225, but these samples did not reach the production number of the "Galaxy". In October 1969, the C-5 set an unofficial world record and took off from Edwards base in California with a weight of 362,063 kilograms.
On December 17, 1969, the first C-5 was handed over to Military Airlift Command for training purposes, and on June 6, 1970, the 437th Military Airlift Wing in Charleston, South Carolina, received its first mission aircraft. By this time, the C-5 program had already been heavily criticized. On the one hand, the costs rose (120 C-5A should cost $ 2.9 billion, Lockheed raised the price to 5.248 billion, the order was reduced to 81 C-5), on the other hand, performance was not achieved. Operation was initially restricted.
By 1973, Lockheed manufactured 81 C-5A aircraft. Up to April 1989, 50 copies of the improved version C-5B with reinforced wing and higher payload, which flew for the first time on September 10, 1985, were delivered. Version C-5C consists of two C-5A converted for the transport of space equipment. With the "Galaxy", the US Air Force had a transport plane with impressive data at its disposal. There was a 985 cubic meter hold that could hold battle tanks and helicopters or up to 345 soldiers. The large, upward-opening gates at the bow and stern enable quick loading and unloading. The undercarriage consists of 28 wheels, making take-offs and landings possible even in unprepared places.
Especially in the Vietnam War, the C-5 had the opportunity to demonstrate its high performance. From the summer of 1970, transports were carried out primarily with heavy equipment: battle tanks and other vehicles for the US Army, but also planes and helicopters. Most recently, it was the C-5 that flew many refugees from South Vietnam at the end of the war. The C-5 was challenged again in the Gulf War in 1991. With 85 aircraft, 42 percent of all air transports were carried out in around 15,800 operations.
The latest version is the C-5M “Super Galaxy”, a modernization of the C-5A / B / C versions that was carried out in January 1999. The "Super Galaxy" received an avionics and a glass cockpit according to the latest status (Avionics Modernization Program, AMP), and in 2001 the order (Reliability Enhancement and Re-engining Program, RERP) was awarded for new electrical systems, a new fuel system and new engines General Electric CF6-80C2 issued with 222 Kilonewton thrust each. The C-5M has a maximum take-off weight of 381 tons and a range of 9,700 kilometers with a payload of 55 tons. The first flight of a fully modernized C-5M took place on June 19, 2006. In view of the high program costs, only 52 C-5A / B / C are to be converted, the remaining 20 or so C-5A / B will be decommissioned. According to the original plans, these measures should be completed in 2014. The first C-5M was delivered to an association in 2009, which received its 18th and last "Super Galaxy" on April 2, 2014. At the beginning of August 2018, the last C-5M left the Lockheed plant in Marietta.
According to the manufacturer, the useful life of the Lockheed Martin C-5M now gained through the modernization will in any case extend to at least 2040 or later. However, the C-5 already has a permanent place in aviation history.