Like most versions of the J79 , the CJ805 and CJ805 - 23 were smoky .
Secondary operator Spantax eventually had their 990 aircraft refitted with smokeless combustion chambers in the 1970s .
Like most versions of the J79 , the CJ805 and CJ805 - 23 were smoky , although secondary operator Spantax eventually had their 990 aircraft refitted with smokeless combustion chambers in the 1970s .