On Tuesday, nearly 950 flights within, into or out of the United States were canceled, according to flight-tracking website FlightAware. More than 1,750 domestic flights have been delayed.
Airlines canceled nearly 1,500 U.S. flights Monday. In total, more than 5,000 domestic flights have been canceled since Christmas Eve as the recent omicron-fueled COVID-19 surge has resulted in crew shortages. Weather in some parts of the country was also to blame, airlines say.
The cancellations come at the busiest time of year for air travel. The Transportation Security Administration said it screened millions of people each day over the holiday weekend, peaking at 2.19 million travelers on Thursday, Dec. 23. On Wednesday, more people passed through TSA checkpoints than on the same day in 2019.
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So far Tuesday, 225 were canceled by SkyWest, 127 by United, 94 by Delta and 82 by Southwest. Seattle-Tacoma International Airport reported 135 origin and destination flight cancelations Tuesday, and Chicago O'Hare International Airport reported 154.
United said it canceled 115 flights Monday, out of more than 4,000 scheduled, due to crews with COVID-19. Delta expected to cancel more than 200 flights out of its schedule of over 4,100, after scrapping more than 370 on Sunday, citing the effect of COVID-19 on crews and winter weather in Minneapolis, Seattle and Salt Lake City.
SkyWest, a regional airline based in Utah, said it had more cancellations than normal during the weekend and on Monday after bad weather affected several of its hubs and many crew members were out with COVID-19.
"We've got to make sure employees don't feel pressured to come to work when they've been exposed to COVID or they think they may have the symptoms," said Captain Dennis Tajer, a spokesperson for the Allied Pilots Association.
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Industry analysts said new guidance from U.S. health officials could help airlines better navigate the impact of omicron on staffing levels. The Centers for Disease Control and Prevention on Monday cut in half the recommended length of time a person should isolate after getting COVID-19 to five days.
Airlines had called on the Biden administration to shorten the quarantine period to alleviate staffing issues caused by omicron, although the union for flight attendants pushed back, saying the isolation period should remain 10 days.
"I definitely think that should help," Raymond James analyst Savanthi Syth said of the CDC's new guidance -- especially if bad weather subsides.
Delta said it was working to implement the new guidance, which would allow the airline more flexibility to schedule employees.
Passengers are urged to check with their airlines and airports for up-to-date information on their flights.
"If you schedule more airplanes than you have pilots for, then that's just a recipe for disappointment on all sides," Tajer said.
The Associated Press and CNN Wire contributed to this report.