BY NORA FELDER: Sunday marked the busiest day at U.S. airports since the start of the pandemicCNN writer Chris Isidore reports. "This year’s traffic was up 4% from the Sunday after Thanksgiving last year, but it’s still down 11% from the same day in pre-pandemic 2019,” Isidore wrote. While there were long lines for the TSA checkpoints, many passengers made it past those checkpoints only to find their flights delayed. Many delays were due to bad weather. Isidore reported that the "combination of fewer available flights and more demand has meant higher fares for passengers.” While there has been an increase of traffic in various airports around the world, flights are expected to return to normal with some delays still being present, according to FlightAware.