Starting Monday, all international travelers including U.S. citizens will need to show a negative COVID-19 test taken 24 hours before departure on any flight headed to the U.S.
At the international terminal at San Francisco International Airport, most of the passengers, who are starting a round trip getaway will be subject to the new tighter testing window when they return.
"24 hours is better than 72 hours because we don't know if people have exposed themselves or gone out after taking that test within the 72-hour window,” said Payal Bagga, who was traveling to India.
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For people with holiday plans abroad, the new rules are another travel challenge.
"I think it's necessary. Although, it has made travel so complicated," said Natalie Raccah, who was traveling to Israel.
Travelers heading out of SFO on international flights will also need to research new restrictions from other countries as well.
France is now requiring a COVID-19 test within two days of departure instead of three.
While Israel is imposing three-day mandatory quarantines for people who arrive in the country.
Public health officials around the world and here in the U.S. are trying to slow the spread of the virus as much as possible.
"I do think that we've made an investment to make sure people aren't bringing new cases especially when we have something like omicron to worry about,” said Dr. Francis Collins, Director of the National Institutes of Health.
The mask mandate for all forms of public transportation will remain in effect until March 8.