It used to be that there was a separate section in the back of the airplane for smoking. Not the ideal situation even for non-smokers since smoke does travel but it’s true that the smoke wasn’t as bad the closer you were to the front. However, on one trip (I can’t recall why; I was with my mom so it may have been the flight to Regina or to/from Vancouver) an old lady wandered to the front of the plane where we were sitting and decided to light up. It’s possible that my memory is exaggerating things after all these years but It seem to recall a fair bit of smoke from that one cigarette. Fortunately the stewardess noticed me coughing (I may have exaggerated my couch a little; can’t recall, but it was definitely bothering me; I think being that high up it was affecting me more than usual). The old lady didn’t get the hint but thankfully that got a flight attendant’s (or stewardess as they were known back then) attention and she moved the old lady to more appropriate seating.