(KTLA) — Beginning Monday, travelers heading to the U.S. will be required to show evidence of a negative test for the virus within one day of boarding their flight instead of three days prior.

Also, President Joe Biden will extend the federal rule requiring passengers on planes, trains and buses to wear face masks through March 18. The rule had been scheduled to expire in mid-January.

The Biden administration’s moves come after the White House announced a ban on travel to the U.S. by foreign nationals who have been to South Africa or any of seven other African countries within the previous 14 days.

That travel ban does not apply to U.S. citizens and permanent residents.

Here’s what travelers should know:

New testing requirements

Starting Monday, the U.S. will begin requiring all inbound international travelers to test for COVID-19 within one day of their flight to the U.S., regardless of their nationality or vaccination status.

That will replace a similar three-day requirement in effect since early November, when the administration scrapped country-specific travel bans.

“This tighter testing timetable provides an added degree of protection as scientists continue to study the omicron variant,” Biden said during a brief appearance to announce his latest measures against the virus.

Do testing requirements apply to children?

Yes, but children younger than 2 do not need to get tested. There is also an option for people who can prove they have recovered from COVID-19 in the past 90 days. Learn more about these requirements.

Do you have to get the test exactly 24 hours before travel?

No. The Centers for Disease Control and Prevention’s policy specifies that travelers must get tested one day before the flight’s departure, but does not say it has to be exactly 24 hours before.

“The Order uses a 1-day time frame instead of 24 hours to provide more flexibility to the air passenger and aircraft operator,” the CDC says. “By using a 1-day window, test acceptability does not depend on the time of the flight or the time of day that the test sample was taken.”

That means if your flight is at 1 p.m. on a Friday, you could board with a negative test that was taken any time the prior Thursday, the agency explains.

Face mask rules

The Transportation Security Administration will extend the requirement to wear a mask on planes, trains, subways and other public transportation including airports and bus terminals through the winter.

Fines, which were doubled earlier this year, will remain in a range of $500 to $3,000.

The mask rule has become a flashpoint on flights, and some in the airline industry are eager to see the mandate go away. Airlines have reported more than 5,000 incidents of unruly passengers to federal authorities since the start of the year, with about three-fourths of the events involving passengers who refuse to wear a mask.

Is testing and quarantine required after arrival?

No, it is not required but the CDC recommends that all travelers get tested three to five days after travel.

Travelers are advised to self-monitor for COVID-19 symptoms and isolate and get tested if they do develop symptoms.

It is also recommended that those who are not fully vaccinated stay home and self-quarantine for a full seven days after travel, even if they test negative within three to five days after arrival.

Unvaccinated travelers who don’t get tested are advised to stay home and self-quarantine for 10 days after travel.

If the traveler has recovered from a documented coronavirus infection within the past 90 days before travel, they do not need to get a test three to five days after travel, even if they’re unvaccinated, the CDC says.

At Los Angeles International Airport, arriving travelers can head to a newly established rapid coronavirus testing site at the airport’s international terminal.