More than 2,000 Christmas Eve flights worldwide have been cancelled at the last minute as a result of the surge in Omicron variant COVID-19 cases.
Among those are 444 flights within, into, or out of the United States, according to the website Flightaware.com.
Airline workers are reportedly among those who are contracting the highly contagious variant.
Delta Air Lines said it had canceled about 90 flights for Friday after exhausting "all options and resources" including rerouting and substituting planes and crews to cover scheduled flights, according to The New York Times.
Delta attributed the cancellations to "a combination of issues" including , potential inclement weather in some regions and the impact of omicron.
United Airlines canceled at least 150 flights set to depart dozens of airports Friday and 44 more scheduled for takeoff Saturday, also according to Flight Aware.
JetBlue, Allegiant and other airlines have also cancelled flights. However, as of Friday morning American Airlines had no flight cancellations.