Is wearing a mask while traveling still helpful if you're the only one?

The Biden administration's mask requirements for airplanes and other mass transit are no longer in effect during a review of a ruling by a federal judge in Florida that struck down the order. Some travelers welcomed Monday's ruling, but others have decided to keep their masks on.

Face masks offer the most protection against the spread of virus-carrying particles in the air when everyone wears them. But research also suggests that masks can protect the wearer alone, by acting as a barrier between particles and their nose and mouth.

"I was actually traveling by plane yesterday when the mask requirement on public transit was removed. I definitely kept my mask on throughout my flight," Chris Cappa, a professor of civil and environmental engineering at the University of California, Davis who studies aerosol particles and masks, wrote in an email Tuesday.