MIAMI, FLORIDA – DECEMBER 28: A sign advises people to wear a mask and stand 6 ft apart as travelers make their way through Miami International Airport on December 28, 2021 in Miami, Florida. Over the holiday weekend, COVID-19 cases in the U.S. reached their highest level in nearly a year. More than 2,000 flights were canceled over the weekend as airlines dealt with a surge in COVID-19 cases due to the Omicron variant. (Photo by Joe Raedle/Getty Images)