The programme has usually been transmitted on Saturday nights , although for a period in the late 1980s and early 1990s it switched to Fridays . The first two series each consisted of 15 episodes ; series 3 ran for 10 episodes ( although one of those episodes was postponed following the death of its guest star , Roy Kinnear ) ; series 4 , 5 and 6 were 12 , 13 , and 15 episodes long respectively . The final episode of series 6 , which focused on a plane crash , was postponed until February 1992 , after being initially scheduled for transmission on 20 December 1991 – one day before the 3rd anniversary of the Lockerbie disaster
Lockerbie disaster
Pan Am Flight 103
Casualty (TV series)