The J-21 Jastreb was developed as a replacement for the
Republic F-84 Thunderjet, which had been the most commonly used turbojet fighter-bomber aircraft of the Yugoslav Air Force until 1967. On the basis of the G-2 Galeb, the J-21 Jastreb was developed as a single-seat, ground-attack variant, flying for the first time on 19 July 1965. Pilots sit on licence-built
Folland Type 1-B ejection seats under individual canopies hinged on the starboard side in unpressurised cockpits. Instruments and controls are entirely conventional with manually operated flying controls and standard flight instruments. Powered by a single BWB licence-built
Rolls-Royce Viper Mk531, the Jastreb has a conventional aluminium alloy stressed-skin structure with few or no special features. The relatively thick aerofoil section, though limiting performance, provides room for fuel cells, and the retracted main undercarriage which retracts inwards, gives the Jastreb a wide track with excellent ground-handling characteristics. The levered undercarriage legs and relatively low-pressure tyres allow the Jastreb to operate from unprepared strips or rough-surfaced airfields. Compared to the Galeb, the Jastreb has a strengthened structure, allowing more weapons to be carried, including three
Browning AN/M3 machine guns, mounted in the nose of the aircraft. Also, the Jastreb is able to carry up to on under-wing pylons, two inner pylons having a capacity of for bombs, rocket launchers, and additional tanks, while the six outer pylons can carry
VRZ-157 rockets. ==Operational history==