The 20th Air Transport Squadron (ATS) was assigned to the 1607th Air Transport Group at Dover AFB, Delaware, in 1955 and flew C-124 Globemaster II aircraft.
In 1963 the squadron transitioned to the new C-141 Starlifter aircraft. It was redesignated the 20th Military Airlift Squadron (MAS) in 1966 and moved to Charleston AFB, South Carolina, in 1973.
The patch depicts the Roman numerals for 20 with clouds above. The Latin motto below reads, “Firmitas Per Mobilitatem.”