I once flew on a Japan Air Lines flight back in the '90s. At that stage they still had the back 6 rows or something as smoking seats. The girl who assigned my seat at check in didn't realise this and allocated me there. I just sat there and took it for 8 hours - nowadays I would have loudly demanded an upgrade out of there - but I was somewhat meek in accepting my fate. The lady next to me had just been to bury a relative in a car crash and was on the way back home. She must have drank half a bottle of whisky and smoked two packets of cigarettes. When I arrived I smelt like a tobacco spitoon and felt as though I had sand rubbed in my eyes.
Allowing smoking on planes was and is a terrible idea. The fire risk alone should immediately discount it.