Credit…David Zalubowski / Associated press

At least 2,100 more flights were canceled globally on Monday, including around 700 flights to the United States, as travel disruptions from one of the busiest weekends of the year for flights spilled over into the work week.

Over the holiday weekend, airlines canceled thousands of flights as the Omicron variant of the coronavirus hit flight crews. In total, around 2,300 U.S. flights were canceled on the Saturday and Sunday of the Christmas holiday weekend, with more than 3,500 more stranded around the world, according to FlightAware, which provides aviation data. As of Sunday alone, more than 1,300 US flights and nearly 1,700 additional flights around the world were canceled.

While some of the groundings were caused by bad weather and maintenance issues, several airlines have acknowledged that the current wave of coronavirus cases, which has increased in the United States to levels not seen since last winter, contributed significantly. A spokesperson for JetBlue said the airline had “seen an increasing number of Omicron sickness calls.”

According to FlightAware, 12% of JetBlue flights, 6% of Delta Air Lines flights, 5% of United Airlines flights and 2% of American Airlines flights were canceled on Sunday.

Southwest Airlines canceled just 68 flights, or 1%, according to FlightAware, and the cancellations were entirely caused by weather conditions, said Dan Landson, a spokesperson for Southwest. “We haven’t had any operational issues related to Covid,” he said in an email.

Stock prices of United, Delta, American and Southwest – America’s four largest carriers – were 1-2% lower in pre-market trading on Monday.

Travel has rebounded strongly this year, worsening the situation at airports: around two million people passed through checkpoints every day last week, according to the Transportation Security Administration. The numbers on Christmas Eve and Christmas Day were much higher than the equivalent numbers last year, and some numbers have even surpassed those on the same days two years ago, when hardly any Americans knew about it. of a virus which then began to circulate on the other side of the world.

There were hints that the worst cancellations could have happened in the United States. For example, Delta planned to cancel about 200 flights on Sunday, less than the 300 it predicted the day before, according to a spokesperson, and only expects 40 cancellations on Monday.

On the flip side, airlines also expect plenty of travel on January 2, a Sunday. And the Omicron variant, which is now responsible for more than 70 percent of new coronavirus cases in the United States, has already helped push daily US case averages above 200,000 for the first time in nearly 12 months, according to The New York Times coronavirus tracker.

A commercial group of airlines has request the Centers for Disease Control and Prevention to shorten the recommended isolation period for fully vaccinated employees who test positive to a maximum of five days, starting at 10 days, before they can come back with a negative test.

“Quick and secure adjustments by the CDC would ease at least some of the staffing pressures and set up airlines to help millions of travelers returning from vacation,” said Derek Dombrowski, a spokesperson for JetBlue. .

The flight attendants union, however, argued that reductions in recommended isolation times should be decided “by public health professionals, not the airlines.”

Some of the delays this weekend had little to do with the pandemic. Alaska Airlines has an extensive program in place to keep crews healthy and has even brought in members of its management team who are trained to be crew members, spokesperson Alexa Rudin said.

On Saturday and Sunday, there were only a handful of cancellations linked to crew exposure to the coronavirus, according to Rudin. Yet it had canceled 170 flights in those two days, according to FlightAware, including 21% of its Sunday flights, due to unusually cold and snowy weather in the Pacific Northwest, which affected its hub, the International Airport of Seattle-Tacoma.