That’s actually not true at all. Bleed air from the engines is constantly pumped into the cabin to maintain pressurization, and what air is recirculated is pumped through HEPA filters. Airplane cabins on a properly maintained modern aircraft have surprisingly clean air.
Ironically, air quality on flights has gone down since the smoking ban since they no longer need to air out and can just recirculate the air.
That’s actually not true at all. Bleed air from the engines is constantly pumped into the cabin to maintain pressurization, and what air is recirculated is pumped through HEPA filters. Airplane cabins on a properly maintained modern aircraft have surprisingly clean air.
https://www.nationalgeographic.com/travel/article/how-clean-is-the-air-on-your-airplane-coronavirus-cvd