Lufthansa Group, Frontier Airlines, Delta, American and United will begin requiring passengers to wear face masks.

Lufthansa policy goes into effect May 4, Delta on May 4, American on May 11  and United on May 4.

The carriers have followed JetBlue‘s lead.

The decision comes as U.S. airlines and regulators are facing increasing pressure from Congress and flight attendant unions to require face masks. However, the DOT, FAA and the five largest U.S. carriers have thus far resisted such calls. Most carriers have begun requiring flight attendants to wear masks.

“This new measure is aligned with CDC recommendations and those of many municipalities within the U.S. that include wearing a face covering when out in public,” Frontier CEO Barry Biffle said.