Douglas C-133A Cargomaster

In early 1950s, the USAF requested Douglas to develop a new airlifter based on the turboprop technology, as an improvement of the C-124. Most significant was its ability to transport intermediate-range Thor and Jupiter missiles. Douglas submitted the XC-132 and YC-133 mock-ups, and the C-133 was selected to go. The Cargomasters went directly into production as C-133A without any prototypes were built. The C-133A made its maiden flight in 1956. In the same year, the USAF requested the C-133 would have to be capable of carrying the Atlas intercontinental ballistic missile just coming into service. It led to the upgraded C-133B that configured with side-opened clamshell door at the back, which allowed for better fitting of the Atlas missile. The first C-133As were delivered to the Military Air Transport Service in 1957 and began flying MATS air routes throughout the world. When the United States involved in Vietnam War, the C-133 was part of the MAC fleet supporting the war in Southeast Asia. The C-133 and C-124 carried outsized loads while the C-135 and C-141 were devoted to higher-priority cargo. After 15 years of service, the C-133s were retired as the Lockheed C-5 Galaxy entered service in 1971.