The Douglas C-54 Skymaster is a four-engined transport aircraft used by the United States Army Air Forces in World War II and the Korean War. Like the Douglas C-47 Skytrain derived from the DC-3, the C-54 Skymaster was derived from a civilian airliner, the Douglas DC-4. Besides transport of cargo, the C-54 also carried presidents, prime ministers, and military staff. Dozens of variants of the C-54 were employed in a wide variety of non-combat roles such as air-sea rescue, scientific and military research, and missile tracking and recovery. During the Berlin Airlift it hauled coal and food supplies to West Berlin. After the Korean War it continued to be used for military and civilian uses by more than 30 countries. It was one of the first aircraft to carry the President of the United States, the first being President Franklin D. Roosevelt during World War II.