WASHINGTON, United States – The United States government is appealing a court ruling that controversially lifted a federal mask mandate on public transport earlier this week, the Justice Department said Wednesday.

After the US Centers for Disease Control and Prevention, the country's top health body, assessed that masks remain "necessary to protect the public health, the Department has filed a notice of appeal," spokesman Anthony Coley said.

A US federal judge on Monday struck down the Covid-19 mask mandate, stating that it exceeded the CDC's statutory authority.

Policymakers in Washington had decided just the prior week to extend it through May 3.

Although the public has a "strong interest" in combating the spread of Covid, the mask mandate "exceeded the CDC's statutory authority," and it "failed to adequately explain its decisions," US District Judge Kathryn Kimball Mizelle of the Middle District of Florida said in her decision.

Multiple major airlines subsequently dropped mask requirements on domestic flights and some international flights, while ride-hailing services Uber and Lyft as well as passenger rail Amtrak additionally announced an end to mask mandates.

When Covid-19 first arrived in the United States in 2020, masks swiftly became one of the defining political issues of the pandemic.

The mask policy across the country has been hodge podge, often left in the hands of local officials. But throughout the federal government has stuck to the mandate on planes, trains and buses.

That has created major headaches for transport staff, especially on planes, who have had to deal with passengers reluctant to mask up -- some of whom have been violent.

The Federal Aviation Administration, the agency in charge of US air transport safety, has received 744 reports of mask-related incidents so far this year.

The government's appeal could create further headaches after the mandate was lifted, and possibly create tensions for travellers if it is reinstated.

The CDC "continues to recommend that people wear masks in all indoor public transportation settings," it said in a statement.

"As we have said before, wearing masks is most beneficial in crowded or poorly ventilated locations, such as the transportation corridor."

The health agency said it would continue to assess the situation to determine whether such a requirement remains necessary in the future.

The United States is currently experiencing another increase in the number of daily Covid-19 cases, linked to the BA.2 sub-variant of Omicron.

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

A YouGov America poll conducted April 18 found 63 percent "strongly" or "somewhat" support US government requirements for masks on public transport.