The MiG-17 is a Soviet transonic jet fighter. It is, in essence, an upgraded MiG-15. Most units have been upgraded to the MiG-17PF standard; its two main differences are its more powerful Klimov VK-1F afterburning turbojet engine and the inclusion of an early RP-1 Izumrud radar. The 17's upgraded airframe allows it to surpass Mach 1 comfortably, thus turning this into a transonic fighter. The MiG-17 has primarily seen action in the Taiwan Strait and over the skies of Vietnam, though it is beginning to appear in the inventories of air forces allied to the Soviet Union, including the OPA Air Force which has begun operating these fighters in its 2nd Air Division.