The 133rd ARS is the group's flying unit and has operated the KC-135R since 1993. The unit was formed as the 133rd Fighter Squadron at Grenier Field, Manchester in April 1947 with the P-47D, and was on active duty between February 1951 and October 1952. It achieved Fighter-Interceptor Squadron status and was equipped with F-51Hs from 1952 until June 1954, when the F-94A/B entered service. The squadron operated F-86Ls from April 1958 until September 1960, when unit became an Air Transport Squadron with C-97As initially and later C-97Gs. The unit was assigned to the 157th ATG and called to active duty in October 1961 for 11 months. The 133rd moved to Pease AFB in 1966, and changed to a Military Airlift Squadron in January 1966 with the C-124C operated from 1968. The unit changed to a Tactical Airlift Squadron in April 1971 with assignment of the C-130A. A further change occurred in 1975 when the unit became an Air Refueling Squadron with the KC-135A, upgrading to the KC-135E in 1984.