The C-124 was the primary heavy-lift transport for United States Air Force Military Air Transport Service (MATS) during the 1950s and early 1960s, until the Lockheed C-141 Starlifter entered service. It served in MATS-gained, later Military Airlift Command (MAC)-gained, units of the Air Force Reserve and Air National Guard until 1974.
First deliveries of the 448 production aircraft began in May 1950 and continued until 1955. The C-124 was operational during the Korean War, and was also used to assist supply operations for Operation Deep Freeze in Antarctica. They performed heavy lift cargo operations for the US military worldwide, including flights to Southeast Asia, Africa and elsewhere. From 1959 to 1961 they transported Thor missiles across the Atlantic to England. The C-124 was also used extensively during the Vietnam War transporting materiel from the U.S. to Vietnam. Until the C-5A became operational, the C-124, and its sister C-133 Cargomaster were the only aircraft available that could transport very large loads.