In the good old days,cough cough, non smokers filled from the front, smokers from the back. Smokers often taking space beyond the half way point.During the flight, if you looked towards the back of the aircraft,it was difficult to see the end for smoke.Visibility was severely restricted. Charter flights were the worst with lots nervous passengers chain smoking.
I flew on an Air France 319 last week, so quite new but, why did it have ash trays?