U.S. airlines called off hundreds of flights for a third day in a row on Sunday as surging COVID-19 infections due to the highly transmissible Omicron variant grounded crews and forced tens of thousands of Christmas weekend travelers to change their plans. 

Commercial airlines canceled 656 flights within, into or out of the United States on Sunday, slightly down from nearly 1,000 from Christmas Day and nearly 700 on Christmas Eve, according to a tally on flight-tracking website FlightAware.com. 

Further cancellations were likely, and more than 920 flights were delayed. 

The Christmas holidays are typically a peak time for air travel, but the rapid spread of the Omicron variant has led to a sharp increase in COVID-19 infections, forcing airlines to cancel flights with pilots and crew needing to be quarantined. 

Delta Air Lines Inc expected more than 300 of its flights to be canceled on Sunday. 

“Winter weather in portions of the U.S. and the Omicron variant continued to impact Delta’s holiday weekend flight schedule,” a Delta spokesperson said in an emailed statement, adding that the company was working to “reroute and substitute aircraft and crews to get customers where they need to be as quickly and safely as possible.” 

When that was not possible, it was coordinating with impacted customers on the next available flight, the spokesperson said. 

Globally, FlightAware data showed that nearly 2,150 flights were called off on Sunday and another 5,798 were delayed, as of 9.40 a.m. EST (1440 GMT). 

Omicron was first detected in November and now accounts for nearly three-quarters of U.S. cases and as many as 90% in some areas, such as the Eastern Seaboard. The average number of new U.S. coronavirus cases has risen 45% to 179,000 per day over the past week, according to a Reuters tally. 

While recent research suggests Omicron produces milder illness and a lower rate of hospitalizations than previous variants of COVID-19, health officials have maintained a cautious note about the outlook.
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