I'd be very surprised to see any airline restrict the use of a medical device onboard. The manual that came with mine states that airlines are required to let you use it, and the manufacturer sells an airline-friendly battery pack. Do you have a link to Delta's policy on this?

My mistake, I was wrong. They allow use, but it has to have its own power supply https://www.delta.com/us/en/accessible-travel-services/assis...

This would seem to be because they don't want to be held to providing medical grade reliability of electricity to the seat.

I've sat next to people using them on Delta and United. Of course, I'm not without empathy for people who depend on them. But if a person has a viral infection that can be spread through droplets, this can be a very dangerous situation. If I'm ever in this situation again, I'll ask to be reseated. If they can't do that, I'm not sure I'd want to fly.

You'd better not let someone sitting next to you breathe, or cough, or sneeze then.

When I'm using my CPAP, my mouth is closed and I'm asleep. I'm breathing through my nose, which has hairy filters in it, plus a mask that has a filter on its exhaust, plus the machine has a filter on its inlet.

Please stop the knee-jerk reactions. CPAP devices and aerosolized droplets are a problem if you know the patient is infected and you are up close to them putting the masks on.

These are not "knee-jerk" reactions.

There's a special, enhanced, risk with CPAP that authoritative medical sources warn about.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338532/

Let's be civil here and assume good faith.