WASHINGTON (REUTERS, BLOOMBERG) - The Biden administration's requirements that people wear masks on US airplanes, public transport, airports and ride-hailing vehicles are not expected to be lifted anytime soon, despite an easing in the rules for mask-wearing elsewhere.

The Centres for Disease Control and Prevention (CDC) announced on Thursday (May 13) that it was easing its guidance for fully vaccinated people, saying they do not need to wear masks outdoors and can avoid wearing them indoors in most places.

But it said workers and travellers should still follow federal requirements to wear masks in transit and in airports and train stations.

There are no requirements that passengers get vaccinated to use transit systems and the Biden administration has opposed the idea of making vaccine passports mandatory.

The Transportation Security Administration (TSA) on April 30 extended face mask requirements across US transportation networks through Sept 13 to address the spread of Covid-19. TSA says transportation system operators have reported almost 2,000 passengers for refusing to wear a face mask since requirements took effect Feb 1.

A TSA spokeswoman said Thursday "we will continue to work closely with the CDC to evaluate the need for these directives."

Airlines for America, a trade group, said US airlines "will enforce the requirement on flights as long as the federal mandate is in place." Earlier this month, the US Federal Aviation Administration (FAA) said airlines have referred 1,300 unruly-passenger reports since February, with most related to not wearing masks, as the agency takes a tough enforcement line and issues hefty fines for noncompliance.

The FAA said Thursday its "zero-tolerance policy toward unruly passengers will remain in effect at least as long as the TSA/CDC face mask mandate is in effect."

Association of Flight Attendants-CWA International President Sara Nelson, representing nearly 50,000 flight attendants at 17 airlines, noted aircraft cabins are "an enclosed, pressurised, and increasingly crowded space as people return to the sky in fewer and smaller airplanes."

She added that "rules for aviation safety are harmonised around the world, and we must have credibility in the safety of flight if the US aviation industry is to regain access to the rest of the world and fully recover."

Meanwhile, House Speaker Nancy Pelosi said masks will still be required for members of Congress and staff on the House floor despite the new guidance from the CDC.

Pelosi issued the mandate last year after many Republicans refused to wear masks during the coronavirus pandemic. The CDC announcement prompted some House Republicans to call on Pelosi and the Office of the Attending Physician to lift the mask rule.

She isn't easing the requirement because its not known how many House members and their staffs are vaccinated, said her spokesman, Drew Hammill.

House members were told earlier this week that they could lower their masks when speaking in the House chamber.

Separately, the attending physician, Brian Monahan, issued guidance relaxing mask and distancing requirements in House office buildings and other areas of the Capitol complex for those who have been fully vaccinated.

"You can resume activities that you did prior to the pandemic," Monahan wrote in a memo.

There was never a mask requirement in the Senate.

Minority leader Mitch McConnell quickly removed his mask after the CDC guidance saying, "free at last" as he walked out of the chamber without a mask.

In a letter to Pelosi Thursday, Representative Tim Burchett, a Tennessee Republican, demanded not only the end of the House mask mandate, but also the virus-related provision to vote by proxy and to conduct virtual hearings.

"It is important that we, as members of Congress, lead by example by returning to normal operations," he wrote.