If someone refuses to wear a mask on a plane, causing the flight to be rerouted/canceled, do they end up on a no-fly list? If so, do the airlines share those lists and add such persons to their own lists? And for how long?
The federal no fly list is supposed to be for terrorists, not for idiots who won’t wear a mask. What is happening is each airline is maintaining their own do not fly lists for this, but they don’t share it with each other. Not sure it really matters, as a serial maskhole would simply wind up on all of lists of their available airlines. Since these lists are airline specific, timeframes are up to their discretion.
If you are also otherwise unruly, you can be fined and even jailed by the feds, but that doesn’t put you on their no fly list.
I probably should have put this one in GQ.
Reported OP for move.
I think it depends on what you do and how the flight crew is feeling. Being particularly disruptive or failing to follow instructions can lead to a charge of “Interfering with a flight crew” which might get you a no-fly-list designation, (much like failing to snitch on your fellow mosque attendees to the FBI could too). Or the airline can just decide they will no longer accept your business. (I’m sure the fine print says if they have to kick you off they don’t have to refund your money, too.)
OP didn’t mention the news story of the 30 teens who refused to wear masks and delayed an entire airplane full of people. Apparently the plane was already delayed and they were sitting inside it with no A/C and felt suffocated. While I don’t support their getting off scot-free, I am going to fly in another 2 weeks and already thinking about mask comfort so I don’t end up having a panic attack myself. Once people start losing it in a confined space like that, things get out of hand very quickly.
Some masks are more comfortable than others. I flew in early April and kept mine on from the time I was picked up at home to the time I was dropped off at my parents’ house, or more than ten hours. (Although I pulled the mask down in the airplane bathroom and in the stall in the airport men’s room.)
Great! Another reason to try to hold my breath in the men’s room. 
I found it slightly ironic that I was using the men’s room as a place to breath without the mask over my mouth and nose.
Right. These people aren’t on a no fly list. They’ve been banned by a private business that happens to be an airline.
FYI, here is an April TSA press release about the mask requirement. Nothing about being added to the no-fly list but it does say, “While this announcement extends the date of enforcement, all other aspects of the requirement remain unchanged, including exemptions and civil penalties. Exemptions to the face mask requirement for travelers under the age of 2 years old and those with certain disabilities will continue. The existing civil penalty fine structure will also remain in place which starts at $250 and rises to $1,500 for repeat offenders who violate this face mask requirement.”
I suspect that the airline will ban you from flying them in the future but that will not extend to other carriers.