The MiG-21UM was the final two -seater version developed from the E-6 UM prototype. It was practically a "US" airframe with improved instruments and avionics up to the "M"and "MF" standards. The new ejection seats were installed, the KM-1U for the front cockpit and KM-1I for the rear cockpit. The distinguish mark is the UHF aerial on the dorsal spine in front of the fin, the attitude sensor on the front nose section and forward -view instructor's periscope installed on the rear canopy frame. This foldable periscope was added because of instructor's requirements to look straight forward during take-off and control the aircraft when it is necessary.