(WWLP) – International travelers are now required to take a COVID-19 test within 24 hours of leaving on their flight to the U.S., regardless of vaccination status.

Previously, vaccinated travelers were required to provide a negative test within three days of traveling. The mask requirement on planes and other forms of public transportation has also been extended until March 18. That was previously set to expire in mid-January.

Experts say they are skeptical of the method intended to slow the spread of the omicron variant.

“As they say, the horse is out of the barn already. So that means to say, even if we put travel bans in other countries, if we continue with what we’re doing in terms of not paying attention to the conditions that may allow this transmission, we are still going to have this transmission in our communities,” said Baystate Health’s Division of Infectious Diseases Dr. Armando Paez.

The Delta variant is still said to be the biggest threat, but with omicron spreading at an alarming rate, the Biden administration is taking steps to tighten air travel regulations.