 The principal purpose for its development was to produce a domestic replacement for the American-built Lockheed T-33 Shooting Star, which at the time was the most commonly used jet trainer aircraft in use by the Yugoslav Air Force; thus, the Galeb was to be capable of meeting the varied qualities and requirements involved in performing "ab initio", intermediate, and advanced instructional training missions.The Galeb was developed as a collaborative effort between Yugoslavia and the United Kingdom, and reportedly contributed significantly to the export value of the latter; a significant proportion of components and ancillary equipment, such as the powerplant, ejector seats, and navigational fittings amongst others, that were installed upon the aircraft had been sourced from or were directly produced by a range of British aerospace manufacturers.Sponsorship for the aircraft's development was provided by the British engine manufacturer Rolls-Royce Limited, whose Armstrong Siddeley Viper turbojet engine was selected to power the type.