NEW YORK (AFP) - Airlines, subways and bus services across the United States moved quickly Tuesday (April 19) to remove mask requirements following a federal court ruling that struck down face-covering mandates on public transportation, a hot-button issue throughout the pandemic.

Uber, Lyft and Amtrak were among the firms that announced an end to masking requirements hours after the decision was released, prompting reactions from travellers on social media.

In one clip, a Delta Air Lines pilot announcing the shift mid-flight is greeted by loud cheers. "Finally!" yells one passenger.

Considerably less enthusiastic was Mr Scott Hechinger, an expert in public defender law, who also heard cheers at the airport, but became increasingly alarmed during the flight.

"There is so much sneezing and coughing. And people just breathing it in. Freedom," Mr Hechinger tweeted.

Policymakers in Washington had decided last week to extend the federal mask mandate through May 3, but a federal judge struck that down on Monday, prompting an immediate wave of announcements from major airlines, including United Airlines and American Airlines.

On Tuesday, both Uber and Lyft shifted to a policy intended to be respectful of those who wish to continue wearing masks, while no longer requiring it.

"While mask usage is still recommended, we've updated our Covid safety policies," Uber said. "Let's move forward, safely together."

Rail company Amtrak also changed its policy, announcing that while masks were no longer required, "anyone needing or choosing to wear one is encouraged to do so."

One prominent transportation provider holding firm was New York's Metropolitan Transit Authority, which will continue to require face coverings on the city's subways and buses, a spokesman said.

In Washington, the Metro bus and rail system lifted its mandate.

The changes come on the heels of Monday's ruling from US federal judge Kathryn Kimball Mizelle who found that the mask mandate exceeds the statutory authority of the Centres for Disease Control and Prevention (CDC).

Ms Mizelle, a nominee of Republican former president Donald Trump, issued her ruling in a lawsuit filed in July 2021 by a conservative non-profit organisation called the Health Freedom Defence Fund and two individual plaintiffs.

Although the public has a "strong interest" in combating the spread of Covid-19, the judge said, the mask mandate "exceeded the CDC's statutory authority," and the agency "failed to adequately explain its decisions."

The Justice Department and CDC said late Tuesday that they disagreed with Ms Mizelle's ruling.

They described the masking order as a "valid exercise of the authority Congress has given CDC to protect public health," according to a Justice Department statement that said potential next steps depended on a CDC public health assessment.

"If CDC concludes that a mandatory order remains necessary for the public's health after that assessment, the Department of Justice will appeal the district court's decision," the statement added.

Polling suggests continued majority support for indoor mask mandates, but with a clear minority opposed.

A YouGov America poll conducted April 18, shortly before the ruling, found 63 per cent "strongly" or "somewhat" support US government requirements for masks on public transport.

Of the remainder, 19 per cent were "strongly" opposed, 10 per cent were "somewhat" opposed and nine per cent weren't sure.

Mask requirements have been a contentious topic throughout the pandemic and have proven particularly nettlesome on planes, where there has been a sharp uptick in assaults of flight attendants.

Flight attendants have been divided on whether to maintain the rule, Ms Sara Nelson, president of the Association of Flight Attendants union said on CNBC Tuesday.

"There's absolutely a sigh of relief from flight crews, but there are also people who are really concerned," said Ms Nelson, adding that the union did not take a position on whether to extend the mandate.

Representative Sam Graves of Missouri, the senior Republican on the House Transportation Committee, applauded Ms Mizelle's ruling.

"It's about time," said Mr Graves. "This hypocritical and overreaching mandate was never about health or science, since mask mandates were gone practically everywhere else. It's time for this mandate to go once and for all."

But Dr Tatiana Prowell, an oncology professor at Johns Hopkins University School of Medicine, said she was hearing from those who are immunocompromised and others with cancer.

"In addition to wearing N95 masks, I'm advising them to travel on less popular days/times if possible during the pandemic for fewer crowds," Dr Prowell said on Twitter.