United Airlines isn’t messing around when it comes to their mask policy. Airline officials announced at the beginning of the week that if you refuse to wear a mask on one of their flights you will be placed on their "internal travel restriction list."
According to an airline spokesperson, "Customers on this list will lose their travel privileges on United for a duration of time to be determined pending a comprehensive incident review."
Flight crew will ask any passenger not wearing a mask when they board to wear one. If they don’t have one they will be offered one. If the passenger still refuses, an incident report will be filed and a formal review will occur. (USA Today)