I recall reading that in some ways air quality was better when smoking in airplanes was legal because they had to cycle air through the outside through ventilation systems.

Now they don't so the air is more stagnant and circulates germs etc.

I have no idea if that's actually the case, or if so, if that's actually better. But it was a point I hadn't considered.

In hindsight, it feels like the sort of "study" that a tobacco company would put out. Like a petrol company funding one that says "climate change is good actually!"