Airlines cancel hundreds more flights on Christmas Day as omicron brings 'COVID-related sick calls'

The total number flight cancellations entering, leaving or inside the United States climbed Christmas Day to 888 and 2,538 worldwide, as airlines struggle to keep planes in the sky amid the surge of COVID-19 cases that are keeping employees off the job.

The numbers Saturday from the flight-tracking website Flightaware.com compare to 690 in the U.S. and roughly 2,000 worldwide on Friday and largely two days ahead of last-minute cancellation notices to booked passengers, upending holiday season travel for the second straight year. 

Delta, United and JetBlue on Friday acknowledged the virus' highly-contagious omicron variant was causing staffing problems that have resulted in flight cancellations. 

United spokesperson Maddie King told the Associated Press on Saturday the staffing shortages were still causing cancellations and when the airline will return normal operations remains unclear – amid one of the busiest travel seasons of the year.  

Delta and JetBlue did not respond to questions Saturday from the wire service.

The three airlines canceled more than 10% of their Saturday scheduled flights. And American Airlines also canceled 90 flights Saturday, about 3% of its schedule, according to the wire service’s analysis of  Flightaware data. 

American spokesperson Derek Walls told the wire service the cancellations are the result of "COVID-related sick calls" and the airline contacted customers Friday.