If you plan to travel this summer — and use any public transportation — don’t forget your mask.

The Transportation Security Administration has extended a federal requirement that travelers on buses, trains, commercial flights and at airports wear face masks. The requirement was set to expire on May 11 and will now be in effect through Sept. 13. The agency started requiring that people over the age of 2 wear masks during flights, on buses, trains and public transportation in February following an order from the Centers for Disease Control and Prevention.

There are exemptions for some disabilities, the TSA said. Fines for refusing to follow the rules start at $250 and go up to $1,500 for repeated violations.

Airlines have required passengers to wear masks for much of the past year as COVID-19 continued to spread but labor unions have pushed the Biden administration for a federal mask mandate to back up cabin crews tasked with enforcing the rules. Carriers have banned more than 2,000 passengers for failing to follow mask requirements., TSA said.

Airlines for America, an industry group that represents most large U.S. carriers, applauded the extension of the mask requirement and said that the “federal face covering mandate has significantly strengthened our flight crews’ ability to enforce these requirements onboard.”

The Federal Aviation Administration in January unveiled a “zero tolerance” policy for unruly travelers after a spike in incidents, many of them involving in travelers who refused to wear masks.