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.