A man looks at the departures board at Salt Lake City International Airport on Friday. Hundreds more flights in the U.S. were canceled on Christmas Day — most involving Chinese airlines, as well as Delta and United in the U.S.

A man looks at the departures board at Salt Lake City International Airport on Friday. Hundreds more flights in the U.S. were canceled on Christmas Day — most involving Chinese airlines, as well as Delta and United in the U.S. / AP

The holiday season travel stress has only escalated amid the rise of the omicron variant. Several airlines are reporting staff shortages from the spread of the coronavirus, leaving passengers with delayed or canceled flights.

According to the flight tracker Flight Aware, 880 flights within, into or out of the United States were canceled on Dec. 25. That's among the approximately 2,521 flights that have been canceled so far today worldwide.

Hundreds of the delayed and canceled flights are coming from China Eastern and Air China, but U.S.-based airlines such as Delta, United and JetBlue are also seeing high cancellation numbers. Delta alone has canceled 290 — or 14% — of its Christmas Day flights.

American Airlines, which canceled 88 flights on Saturday, told NPR in a statement that their operations have been "running smoothly" but that COVID-related sick calls led them to pre-cancel some of their scheduled flights for the day. Affected customers were notified yesterday, they said.

While airline travel was starting to pick back up before the omicron variant emerged, the massive spike in positive COVID-19 cases seen in recent weeks has become a cause for concern to airlines in keeping airline staff and passengers safe.

Lawmakers, including Sen. Dianne Feinstein (D-Calif.), are calling on the the Centers for Disease Control and Prevention and the Federal Aviation Administration to make a major change and require proof of vaccination or a negative COVID test in order to travel on all domestic flights.

"Ensuring the health and safety of air travelers and their destination communities is critical to mitigating the ongoing COVID-19 surge, especially as the virus continues to evolve," the lawmakers wrote in a letter to the CDC and FAA on Monday.

"Requiring proof of vaccination or a negative test for domestic flights would improve public health and address concerns that passengers have about flying," the letter said.

Vaccination protocols for international travelers coming into the U.S. are already in place, according to the CDC.

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Tags: flight cance  United Airlines  Delta Air Lines  American Airlines  Series: The Coronavirus Crisis