On board filtration systems were optimized after past airborne pandemics on board pandemics. I'm not worried about covid on flights. If they weren't, you would smell every fart everybody on a 200 person flight had.
Concourses are another issue. Some are different from others, and connections that force you onto shuttles are an issue too. Flying through ORD last year, I remember smelling a restaurant from several hundred yards away. I knew then the ventilation there was no good. JAX, DTW were fine.