Masks return, COVID delta variant spreads Masks make a comeback as delta variant spreads While airports never stopped requiring masks, many retailers did. Now, some are shifting gears as the COVID delta variant spreads. MILWAUKEE - Masks are making a comeback thanks to the quick spread of the COVID-19 delta variant. Milwaukee Mitchell International Airport is one place that never stopped requiring you to mask up. The TSA's mask requirement, which applies to airports, airplanes, commuter bus and rail systems, currently runs through Sept. 13, but a TSA spokeswoman said it's possible that is extended. "Personally, I don’t see a downside for wearing them," said Richard Glassman, traveler. "It’s controversial, I understand."