 Complete the following phrase:  The squadron was activated in 1967, and took over DeHavilland Canada C-7A Caribou aircraft that were formerly operated by the 17th Aviation Company of the U.S. Army in South Vietnam, adopting the tactical airlift mission. The squadron initially maintained a detachment at An Khe, which had been the 17ths base. It operated from Phù Cát Air Base. The 537th earned a Navy Presidential Unit Citation, as well as an Air Force Presidential Unit Citation for airlift support of 