Globally, airlines have canceled over 2,000 flights, 454 of which are within, into or out of the United States.
Operational snags at airlines are coming as millions are still flying in spite of rising coronavirus cases. The TSA says it screened 2.19 million people at airports across the country on Thursday, the highest figure since the uptick in holiday travel started a week ago.
Hundreds of US flights canceled
On Thursday, United Airlines said it had to "cancel some flights" because of the omicron variant of the coronavirus.
"The nationwide spike in Omicron cases this week has had a direct impact on our flight crews and the people who run our operation," said a United memo obtained by CNN.
United has canceled 170 flights, representing 9% of its total schedule, according to flight tracking site FlightAware.
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United said it is "notifying impacted customers in advance of them coming to the airport," according to a company 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."
Later Thursday night, Delta Air Lines also canceled flights. The airline has canceled 130 Christmas Eve flights, according to FlightAware.
Delta said the cancellations are due to multiple issues including the omicron variant.
"We apologize to our customers for the delay in their holiday travel plans," Delta said in a statement. "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."
Additionally, JetBlue canceled more than 50 flights, or about 5% of its overall schedule.
Alaska Airlines said in a statement that it canceled 17 flights because of omicron Thursday and more cancellations are possible on Christmas Eve. So far, it has canceled 11 flights Friday.
Thousands of international flights canceled
China Eastern has canceled 474 flights, or 22% of its operation, according to FlightAware. Similarly, Air China canceled about 190 flights, or 15% of its schedule.
Air India, Shenzhen Airlines, Lion Air and Wings Air all canceled dozens of flights as well.
- Andy Rose, Sharif Paget and Ramishah Maruf contributed to this report
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