A Biden administration mandate on mask wearing on all public travel or transit within, into or from the U.S. takes effect at 11:59 p.m. Eastern time Monday.
The wide-ranging order applies to passengers and operators of planes, ships, ferries, trains, subways, buses, taxis and ride-shares as well as within transportation hubs, including airports, bus and ferry terminals, train stations and more.
The order applies to international travel, interstate travel and travel within states, Martin Cetron, the CDC's director of global migration and quarantine, wrote in an order issued late Friday.
Exceptions to the mask requirement will be allowed for children under age 2 and for people who cannot safely wear a mask due to health conditions.
Travelers will still be allowed to remove masks in order to eat or drink and, if necessary, to communicate with someone who is hearing impaired.
The CDC order does not clarify the penalties travelers and transport operators will be subject to for lack of compliance. A TSA press release on Sunday said that those who refuse to wear a mask at airport screening "may be subject to a civil penalty."
Most travel providers around the country already require masks.
The federal mandate will be in effect until further notice.
Update: This report was updated to clarify that the start time on enforcement was Monday, Feb. 1.