The 1st Squadron of the 18th FAR transitioned to the supersonic MiG-19S/P in 1963. The following year saw a group of the regiment's flight officers being dispatched to the USSR for an operational conversion course to the advanced MiG-21 fighter. Upon arming with the MiG-21PF aircraft (12 units) the 2nd Squadron was transferred to the Gabrovnitsa Airfield in the country's northwestern area. After an upgrade in 1969, the regiment's MiG-19P were brought to a standard, which allowed them to carry two K-13 Air-to-Air missiles with IR-homing.