In a bid to survive, airlines are desperately trying to convince a wary public that measures like mandatory face masks and hospital-grade air filters make sitting in a plane safer than many other indoor settings during the coronavirus pandemic. It isn’t working. Surveys indicate that instead of growing comfortable with air travel, more people are becoming skeptical about it. In the United States, airline bookings have stalled in the past month after slowly rising — a reaction to a new surge of reported virus infections. Globally, air travel is down more than 85% from a year ago, according to industry figures. The implications for the airline industry are grave.