The rules are mostly random except everyone now bans bandanas and balaclavas, which the CDC loudly endorsed in April of 2020:
Learn what some domestic airlines prohibit passengers from wearing to comply with the TSA mask mandate.
Source: Several Airlines Now Banning Cloth Face Coverings During Flights – TravelAwaits
Finnair mandates N95s and has banned all cloth facial coverings. Many now recognize that cloth facial coverings were largely useless. Public health should have developed standards for effective facial coverings – a random bit of cloth is NOT an N95 – bits of cloth have 0% to 25% effectiveness and there is on evidence they have reduce the spread of the disease.
