United Airlines and Delta Air Lines have said they had each cancelled dozens of Christmas Eve flights, as the spreading Covid-19 Omicron variant takes a toll on its flight crews and other workers.

Chicago-based United cancelled 120 flights for Friday, while Atlanta-based Delta said it has canceled about 90, Reuters reported.

“The nationwide spike in Omicron cases this week has had a direct impact on our flight crews and the people who run our operation. 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.

Delta said it has “exhausted all options and resources — including rerouting and substitutions of aircraft and crews to cover scheduled flying — before cancelling around 90 flights for Friday.”