The Omicron variant of the coronaviruses caused airlines to cancel nearly 1,000 flights on Christmas Day.
More than 10 percent of the flights scheduled by Delta Air Lines, United Airlines and JetBlue were affected by the cancellation. According to FlightAware, American Airlines canceled less than 5 percent of flights.
The number of canceled flights exceeded the total on Christmas Eve, a blow to travelers and airlines hoping for a return to normal. More than 2,500 flights were canceled around the world on Christmas Day.
A number of Covid-related sick calls led to the cancellation of some flights on Saturday, according to a spokesman for American Airlines. We are working hard to rebook the affected customers.
The problems are expected to get worse. The weather in some parts of the country is causing problems for Delta, which is expected to cancel more than 300 flights on Sunday. The FlightAware website said that other airlines had already canceled flights.
During one of the busiest travel periods of the year, Americans are flying nearly as much as they were prepandemic, with about 2 million people streaming through screening checkpoints each day in the week leading up to Christmas Eve, according to the Transportation Security Administration. The number of travelers this year exceeded the number of passengers who flew, according to the T.S.A.
During the travel period there was a surge of Covid cases. According to The New York Times, the US has an average of 200,000 new cases each day, more than the average case load during the summer.
An airline trade group asked the Centers for Disease Control and Prevention to shorten the recommended isolation period for employees who test positive for Covid-19 from 10 days to no more than five days. The group, Airlines for America, wrote a letter to the C.D.C. director, saying that the Omicron surge may cause shortages and disruptions.
The C.D.C. was told by the Association of Flight Attendants that the decision to reduce isolation times should be made by public health professionals.
