With take-home tests hard to find and testing demands creating long lines nationwide, other safety measures such as wearing N95 or KN95 masks while traveling for the holidays will be critical, said Dr. Esther Choo, associate professor at Oregon Health and Science University.

Flying has an increased risk due to a lack of vaccine requirement and an inconsistent adherence by some to fully keeping on their masks, such that "this could be a much safer activity than it currently is," Choo told CNN's Laura Coates on Thursday.

"Speak up when you see those around you not wearing masks. This is not a time to be polite and let people do what they feel like doing. It's really about keeping everyone safe," she said.

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By Travis Caldwell, CNN

Updated 11:54 AM ET, Fri December 24, 2021