From CBS News:
“United and Delta have canceled more than 200 flights on Christmas Eve as a surge in COVID-19 cases impacts their staff.”

“The nationwide spike in Omicron cases this week has had a direct impact on our flight crews and the people who run our operation,” a United Airlines spokesperson told CBS News in a statement. “As a result, we’ve unfortunately had to cancel some flights and are notifying impacted customers in advance of them coming to the airport.”
Top Copyright Photo: United Airlines Boeing 757-324 WL N75854 (msn 32813) LAX (Michael B. Ing). Image: 958215.
United Airlines aircraft slide show:
United Airlines aircraft photo gallery:

https://twitter.com/united/status/1473365734671716369?s=20

