Airplanes have about 12-15 air changes per hour they are flying, and the air that is recycled, less than half, is going through standard HEPA filters and are rated to capture virus and bacteria particles.

My less empirical info is that airflow in a plane mostly goes from being input above your head, and exhausted from the pressurized cabin at your feet, meaning you have less exposure to anyone not in your row.

Remember that aircraft pressurization systems were designed to be smoked in, other than the newest designs. They needed enough airflow to not totally choke out passengers on a cross country or cross atlantic trip.

If only saving a quick dime wasn't the main goal and maybe improving the comfort of cattle class.

Most systems lead to a dry throat due to bad filter designs and improper humidity regulation which is a shame.

Are you able to square the levels of CO2 on planes, which are 1000-1800 ppm, so over 2-3x atmospheric air, with the 12-15 ACH? I don't understand how those two things can be true.

ACH often refers to filtration and not ventilation; that is, recycled air counts for ACH calculations but won't decrease CO2 because that's not scrubbed by the filters. So it's possible you can have high CO2 levels but also no virus or particulate matter in the air; this is why some places will report PM2.5 as well as CO2, as a proxy for filtration. To make it more complicated, you can also use UV-C to inactivate pathogens, which may not decrease PM2.5 and won't decrease CO2.

I'm not saying this is the case necessarily for planes, but I'm just trying to provide context for how proxy measures of air quality may not tell the full story.

IIRC the airlines did improve filtering of air in the cabin, but I think this is basically moot - you’re stuck in a hermetic, pressurized can with hundreds of other people and some percentage of them is exhaling viral droplets into the air that’s force circulated through the cabin. Unless you’re wearing a hazmat suit, you’ll be exposed.

I'm not talking about viral/bacterial factors here, clearly a better filter with a better humidity system doesn't cause you to end up with a dry throat. I'm not talking about exposure to people your in the same goldfish bowl as, that's a guaranteed to happen when you bump into people getting your bags outside...