In an executive order he will issue Thursday, his second day in office, Biden will codify an action by former President Donald Trump on Jan. 12 to require a negative Covid-19 test before flying to the U.S. from other nations, according to a Biden administration fact sheet. The order will be coupled with one requiring masks on federal properties that was signed by Biden on Wednesday.

The language of the orders hadn’t been released so it’s difficult to assess how the various provisions will be enforced. All U.S. carriers have some kind of requirement that passengers cover their faces, as do many airports and transit systems.

But the federal mask requirement could put teeth into policies now written and enforced by the airlines, which have limited remedies, such as refusing to allow customers to board future flights.

And it will go beyond airplanes. According to the Biden fact sheet, the administration will require “mask-wearing in airports, on certain modes of public transportation, including many trains, airplanes, maritime vessels, and intercity buses.”

While evidence on the risks of flying during the pandemic varies, there is broad consensus that wearing a tight face covering can significantly reduce the risks of transmitting the Covid-19 virus.

One of the actions with the highest potential impact is a requirement that people arriving in the U.S. from other nations adhere to what have previously been unenforced quarantine guidelines from the Centers for Disease Control and Prevention.

The CDC suggests international travelers get a second test for the virus within three to five days after arrival and that they stay at home or in isolation for seven days — even if the test is negative. For people who don’t get tested, it’s safest to isolate for 10 days, the CDC says.

Similar restrictions in the U.K. have reduced travel and have been opposed by airlines and others in the travel industry, who have said aggressive testing should be enough to slow spread of the disease.

“The Executive Order also calls for the consideration of additional public health measures in domestic travel,” according to the Biden fact sheet.

Adherence to the airline mask requirements have at times been spotty, and there are exceptions for when passengers must eat and drink. Aside from persuasion, the only tool for airlines if passengers refuse is to prohibit them from taking the flight.

Mask Rules

The new Biden policy could subject passengers to charges. During the entire pandemic, the Federal Aviation Administration has only filed civil charges against two people related to their refusal to wear masks in cases of alleged threats or assaults on flight attendants.

Hundreds of people have been barred from flying on individual carriers for refusing or getting into disputes with flight attendants and pilots over the issue.

In the days surrounding the Jan. 6 pro-Trump mob storming of the U.S. Capitol, numerous incidents were reported on social media and by airlines of people traveling to and from Washington without masks.

The two most senior Republican senators overseeing aviation policy, Mississippi’s Roger Wicker and Texas’ Ted Cruz, were both photographed on planes without masks last year. Wicker served as chairman of the Commerce, Science and Transportation Committee and Cruz was the leader of the Aviation and Space subcommittee.

Flight attendant unions had been particularly vocal in demanding more action by the government, saying it was unfair that their members had to enforce a rule without teeth.

“Masks are effective in dramatically reducing the risk of spreading Covid-19,” said Sara Nelson, president of the Association of Flight Attendants-CWA, in a press release last July. “But they are only effective if everyone does their part in properly wearing the masks.”

Travel Ban

Materials summarizing the Biden executive order made no mention of a separate ban on the arrival of most European and Brazilian travelers. Trump announced Monday that he planned to rescind the orders, most of which were enacted last March.

But Biden spokeswoman Jen Psaki said that day the incoming administration plans to block Trump’s move.

“On the advice of our medical team, the Administration does not intend to lift these restrictions on 1/26. In fact, we plan to strengthen public health measures around international travel in order to further mitigate the spread of Covid-19,” she tweeted.

The new order comes the same day that U.S. infectious-disease chief Anthony Fauci pledged his country’s commitment to the World Health Organization, including membership in a global effort to deploy Covid-19 vaccines.

Fauci addressed the Geneva-based group Thursday morning, underlining the new president’s effort to mend ties with an agency crucial to fighting the pandemic. He confirmed that the U.S. will join Covax, a 92-nation vaccine collaboration that the Trump administration declined to participate in.