DENVER (KDVR) — United Airlines and Delta Airlines have canceled several dozen flights on Christmas Eve, at least in part because of impacts from the omicron variant.

United Airlines said it has canceled about 120 Christmas Eve flights across the company’s flight network. That number had grown to 136 by Thursday evening, including 13 at Denver International Airport, according to FlightAware.

Delta Airlines has canceled 92 flights by the same time, including four at DIA.

United Airlines said its cancellations were because of COVID-19 impacts on the company’s staff and flight crews.

“The nationwide spike in omicron cases this week has had a direct impact on our flight crews and the people who run our operation,” United Airlines said in a statement Thursday evening. “As a result, we’ve unfortunately had to cancel some flights and are notifying impacted customers in advance of them coming to the airport. 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.”

Delta Airlines also blamed the impact of the omicron variant, as well as possible inclement weather in some locations.

“Delta teams have exhausted all options and resources — including rerouting and substitutions of aircraft and crews to cover scheduled flying — before canceling around 90 flights for Friday,” the airline said in a statement. “We apologize to our customers for the delay in their holiday travel plans. Delta people are working hard to get them to where they need to be as quickly and as safely as possible on the next available flight.”