The MiG-21U was developed based on the MiG-21 F-13 fighter aircraft. The combat trainer version was equipped with, among other things, the SPU-7 onboard intercom, the KAP-2 autopilot, and a damage simulation device, while the fuselage-mounted cannon was removed. The MiG-21U was produced between 1962 and 1968. In NATO code, the MiG-21U was designated Mongol A.
Poland purchased 11 aircraft between 1965 and 1966, of which 6 were of the 66-400 variant and 5 of the 66-600 variant. They remained in service until 1990. The MiG-21U 66-400 specimen, serial number 161217, was delivered on 29 June 1965. It was operated by the 40th Fighter Aviation Regiment in Swidwin and subsequently by the 1st Fighter Aviation Regiment in Minsk Mazowiecki. In 1990, it was transferred to the Polish Aviation Museum.
| Wingspan | 7.15 m |
| Length | 12.18 m |
| Takeoff weight | 7800 kg |
| Maximum speed | 2175 km/h |
| Ceiling | 18300 m |
| Range | 1460 km |
| Armament | A-12.7 mm machine gun in an underfuselage pod |
| Engine | R-11F-300 turbojet with 5740 kG thrust |
