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-1Ufor 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