Multiple airlines across the United States canceled hundreds of flights on Christmas eve, citing a nationwide surge in Omicron cases which has directly impacted employees and flight crew.

The cancellations come as more than 109 million Americans are expected to travel 50 miles or more via airplanes and other forms of transportation to visit friends and family over the festive period.

That figure is an almost 34 percent increase from 2020, with 27.7 million more people traveling than last year, bringing the number of people traveling during the season to pre-pandemic levels, according to the American Automobile Association (AAA).

According to Flight Aware, which provides real-time flight tracking data, United Airlines canceled 150 flights on Friday while Delta canceled 99.

A spokesperson from United Airlines told ABC News that the nationwide spike in Omicron cases this week has directly impacted flight crew and employees.

“As a result, we’ve unfortunately had to cancel some flights and are notifying impacted customers in advance of them coming to the airport,” United said in a statement. “We’re sorry for the disruption and are working hard to rebook as many people as possible and get them on their way for the holidays,” the airline added.

United Airlines spokesperson Joshua Freed told The New York Times that flights could potentially be canceled on Christmas Day.

“We are really managing this day by day,” Freed told the Times. “There may be some more flight cancellations for Saturday. It’s possible.”