When I was on my job interviews 25ish years ago, I happened to be at an airport bar where a very tan 60-something with a very expensive watch was next to me. A bit of talking, and he was a America-to-Europe commercial pilot. Great guy. He tells me a story:
"At the old airports, go look at the tarmac. You will see two big dark spots on the ground where the ass-end of the plane is. Why? Because when everyone smoked on flights, and when the air in the plane circulated through the plane and went out the back, once we got close to landing, that shit would condense and drip out of the ventilation shafts".
The tar/nicotine was so thick in those planes they would drip on to the tarmac.