The Transportation Security Administration announced Thursday that masks would continue to be required on all transportation modes through mid-March.
On its website, the agency said the mandate would be in place through Sept. 18.
Masks will continue to be required at "airports, onboard commercial aircraft, over-the-road buses, and on a commuter bus and rail systems."
News of the mask extension by TSA comes as the Biden administration released details on efforts to combat the Omicron variant, which was discovered by scientists in South Africa last week.
On Wednesday, U.S. health officials announced that a person in California had become the first in the U.S. to have an identified case of the omicron variant.
Clusters of cases have been identified in Hong Kong, Australia, Portugal, and Canada.
TSA began requiring travelers to wear masks in airports and during flights on Feb. 1.