and light attack roles. As built, the Saab 105 was typically powered by a pair of Turbomeca Aubisque low-bypass turbofan engines, licence-manufactured by Volvo Flygmotor as the RM9. The Aubisque engine reportedly provided favourable engine-out characteristics, allowing the aircraft to proceed to successfully takeoff in the event of a single engine failing at the critical point. This has not been the sole powerplant for the type, as a number of 105 aircraft have been powered by the General Electric J85 engine instead. Swedish Air Force aircraft have been remanufactured during the 1990s to use the newer Williams International FJ44, which has been designated as the RM15. Operational history In July 1967, the first Swedish Air Force student pilots started training on the Saab 105. In July 1970, Austrian Air Force pilot training activities on the type formally commenced; by August 2010, 22 of Austria's Saab 105 aircraft remained operational, attaining a combined total flight time of roughly 1,500 flying hours per year. During the 1990s, by which point the existing engines of the Swedish Air Force's Sk 60 fleet were considered to be towards the end of their technical and economic lifespan, it was decided to replace the Turbomeca Aubisque engines with newly built Williams International FJ44 engines, which are lighter and less costly to operate. In November 1993, a contract was signed for the re-engining of 115 aircraft; the number of aircraft to be upgraded was subsequently reduced as a result of cuts to the defence budget. The replacement was performed as a low-cost measure to fulfill the Swedish Air Force's continuing requirement for a primary trainer aircraft. In September 1996, the first of these upgraded aircraft, which had been redesignated as the Sk 60W, was re-delivered to the Swedish Air Force. In June 2007, Saab signed a long term service agreement with the Austrian Air Force to provide logistics and technical support for their Saab 105Ö fleet for a further 10–15 years. Austria finally retired the Saab 105 on 31 December 2020. In December 2008, Saab received a SKr900 million ($115 million) contract to support extended operations of Sweden's 105 trainer fleet up to mid-2017. In September 2009, a SKr130 million ($18.8 million) contract to deliver a package of cockpit and system upgrades for the Sk 60 aircraft was signed. One goal of this modernisation was increased compatibility with the Saab JAS 39 Gripen, the primary combat aircraft