More than 2,800 flights cancelled, 12,000 delayed globally on Thursday

More than 2,800 flights were cancelled and nearly 12,000 more were delayed around the world on Thursday as the Omicron variant of the coronavirus caused staff shortages at airlines, the tracking website FlightAware showed.

"We strongly urge flyers with non-essential travel scheduled before January 2, 2022, to consider changing their travel to a later date using our flexible travel policy," the airline JetBlue said in a statement, encouraging passengers to think about rescheduling nonessential flights during the holidays.

JetBlue said it expects the number of cases to surge in the US northeast, where most of its crew are based.

Along with the Omicron variant overrunning the United States and sickening flight crews, winter weather has caused numerous flight cancellations.

Health officials have acknowledged that the Omicron variant is more transmissible but the cases are mild and no deaths have so far been reported.