A-10 Thunderbolt IIs prep for flight Published Dec. 4, 2012 By Staff Sgt. Craig Cisek 51st Fighter Wing Public Affairs OSAN AIR BASE, Republic of Korea -- The first production of A-10s was designed specifically for close air support in 1975. A-10 Thunderbolt IIs are attached to the 25th Fighter Squadron at Osan Air Base. The squadron was activated under the 51st Fighter Wing at Osan Oct. 1, 1993. Today the aircraft remains the leading close air support fighter for the peninsula.