Sunday marked the busiest day at US airports since the start of the pandemic — and though bad weather caused widespread flight delays, relatively few flights were canceled outright. About 2.6 million people were screened at Transportation Security Administration checkpoints Sunday. That’s the most since December 26, 2019, just a couple of months before the pandemic’s arrival stateside caused a near halt in air traffic. 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. Unfortunately for passengers, once they made it through the TSA checkpoints they found widespread delays mostly related to weather. US airlines had 6,600 delayed arrivals on Sunday, according to tracking service FlightAware — about 26% of scheduled flights — with the average delay at about 51 minutes. Still, only 178 flights by US airlines were canceled altogether on Sunday, representing less than 1% of scheduled flights. Earlier in the summer, airlines were forced to cancel a much higher percentage of flights, especially around busy holiday weekends, due to staffing shortages. About 3% of flights were canceled on the Saturday of Independence Day weekend 2022, and 5% of flights were canceled on the Fridays before both Memorial Day and Father’s Day/Juneteenth weekends this year. New Year’s weekend was far worse, however, when between 8% and 13% of flights were canceled each day as a surge in Covid cases caused many airline employees to be unable to work. Because of those service meltdowns, US airlines have trimmed the number of flights on their fall schedules to increase reliability. The number of scheduled fights Sunday was down 2% compared to the same day last year, according to FlightAware. The combination of fewer available flights and more demand has meant higher fares for passengers. That’s likely to be the case through the rest of this year, which is poised to be the most expensive holiday travel season on record. After this Sunday’s delays, flights appeared to be returning to normal Monday with only 658 delays reported by FlightAware as of 8 am ET.