F21 in Lulea didn't have any Viggen (AJ37, JA37, J37 or A37) until 1979. At 1972 they still used the airplane Draken (J35).
Second, the plane that gets blown up in the beginning of the film is a SK37 Viggen, its a double seated airplane for educational use. They have tried to mask it as an ordinary Viggen, but failed. There is a bump after the flight deck that is not on combat models