The early MiG-21 fighter variants, MiG-21F and MiG-21F-13, were clear-weather daylight-only fighters. Although they were in use with the Soviet Air Force Frontal Aviation (VVS FA), due to their limitations, they were unsuited for the interception tasks of the Soviet Air Defence Forces (PVO).
The MiG-21F and MiG-21F-13 fighter variants, which could only operate in clear weather, were used by the Soviet Air Force Frontal Aviation (VVS FA). However, due to their limitations, they were not effective for intercepting tasks of the Soviet Air Defence Forces (PVO).