The G-4 Super Galeb was developed as a replacement for the G-2 Galeb, which had been the most commonly used jet trainer aircraft of the Yugoslav Air Force up until 1985. The first of two prototypes was completed by early 1978. Following completion of the initial testing phase, the first flight was achieved on 17 July 1978 and the first of six pre-production aircraft on 17 December 1980. These and the first prototype were designated G-4 PPP, and had fixed tailplanes with inset elevators and no anhedral. Production examples (and the second prototype) were designated G-4 and featured an all-moving anhedral tailplane and comprehensive avionics improvements. The G-4 first flew in 1983 and has been ordered in large numbers for the Yugoslav Air Force. The G-4 features a low wing monoplane design with slightly tapered wings. The aircraft is 12.25m long and 4.3m high, with a wingspan of 9.88m. It weighs 3,250 kg when empty and can carry 1,882 kg of fuel. The aircraft is fitted with a short nose cone, rounded fuselage, conventional empennage, semicircular air intakes, vertical tailfins, rudder, ailerons, horizontal stabilisers and fuel tanks at the square tips. The G-4 its performance is considerably improved by the introduction of a more powerful version of the Rolls-Royce Viper 632-46 turbojet. The cockpit is fitted with two ejection seats with the rear seat slightly elevated to render all round clear visibility.
G-4 : Advanced jet trainer and light ground-attack aircraft.
G-4Š : Unarmed jet trainer.
G-4T : Target puller.
G-4M : Upgraded avionics and hardpoints, missile rail added to wingtips. Avionics include a Zrak ENP-MG4 HUD incorporating a Rudi Cajavec ENS-MG4 electronic sight, a gyro platform, multi function displays, and an optional chaff/flare dispensers. The inner hardpoints are rated at 500 kg, while the outer ones are rated at 350 kg, giving a maximum disposable load of 1,800 kg. Normal takeoff weight is 4,971 kg as a trainer, with a maximum takeoff weight of 6,400 kg in the attacker configuration, the maximum speed in "clean" configuration is 865 km/h at 10,000 m and 900 km/h at 4,000 m, with a ferry range of 2,900 km with drop tanks; range of 1,800 km with standard fuel, reduced to 1,200 km with cannon pack, four BL755 cluster bombs and two AAMs, maximum rate of climb at sea level of 1,800 m per minute, and a service ceiling of 12,500 m.
G-4MD : Further development of G-4M upgrade including: LCD flight screens, HOTAS, HUD, integrated mission computers, distance measuring equipment, GPS-based navigation systems, identification friend or foe, navcomm units, mission records, and VHF omni-range and instrument landing systems. Integration of guided weapons, countermeasures and targeting systems is also scheduled as part of the upgrade.