To gain experience with jet aircraft, ahead of the Saab 29 Tunnan project, Saab converted four Saab J21As with jet engines, to become J21R. Unfortunately, no J21R aircraft were saved after the type was retired at the end of the 50s. The museums J21A 21286 had no engine and was chosen to be rebuild as a J21R. The aircraft was handed over to the museum on 13 April 1998 as a J21R.