The 155th AS is the group's operational unit and has flown the C-141B since early 1992. The 155th Fighter Squadron formed in December 1946 with P-51Ds and was mobilized in April 1951 as the 155th TRS, flying RF-51Ds. The 155th was demobilized in January 1953 with the RB-26C and converted to the RF-84F in April 1956. The unit became the 155th Air Transport Squadron with C-97Gs in April 1961 and was joined by the 164th ATG. The unit was redesignated the 155th MAS in January 1966 and switched to the C-124C in May 1967. It became the 155th TAS in August 1974 with the C-130A and was last the US unit to operate that version of the Hercules.