Travelers who have been able and determined to keep their Christmas plans despite the rapidly spreading omicron strain of COVID-19 have run into a new stumbling block: cancelled flights.

As the new version spreads over the world, a growing number of airlines have been forced to postpone flights, putting thousands of people’s holiday vacation plans on hold.

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According to flight tracking website FlightAware, worldwide airlines had together cancelled almost 2,000 flights as of Friday morning.

At least 454 flights were scheduled inside, into, or out of the United States when they were cancelled.

Due to the omicron variation impacting personnel and crew, a number of airlines, notably United Airlines, Delta, and Alaska Airlines, have been forced to cancel hundreds of Christmas Eve flights.

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United Airlines said it had to cancel 112 flights on Friday as the virus spread throughout the country, affecting its workers.

The airline claimed in a statement, “The nationwide spike in omicron cases this week has had a direct impact on our flight crews and the people who run our operation.”

It promised to rebook as many passengers as possible.

Delta Air Lines apologised for postponing 90 flights scheduled for Friday, blaming the omicron variant and potentially severe weather in cities like Seattle and Salt Lake City.

“Delta teams have exhausted all options and resources — including rerouting and substitutions of aircraft and crews to cover scheduled flying — before canceling,” the airline said in a statement Thursday.

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After several employees reported suspected exposure to COVID, Alaska Airlines cancelled 17 flights on Thursday. Additional cancellations were anticipated on Friday “due to this dynamic scenario,” according to a statement from the airline.

No cancellations were planned, according to an American Airlines representative. Inquiries about Friday’s programme were not immediately returned by other airlines.

Meanwhile, Lufthansa has had to cancel a number of long-haul transatlantic flights owing to illness among its crew members, however a representative for the airline told NBC News that they couldn’t confirm whether the illnesses were caused by COVID.

“Currently there is a massive increase in sick leave,” a spokesperson said. “Therefore, we have canceled individual flights across the North Atlantic, e.g. to Washington, Boston and Houston from Frankfurt.” They claimed they were working on getting travellers rebooked on other flights.

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According to the trade association Airlines for America, despite the fact that the holiday season attracts more air travellers, Christmas Eve is usually one of the quietest days of the stretch.

According to the group, Thanksgiving weekend travel in the United States increased to roughly 90% of pre-pandemic levels.

Holiday air travel is expected to roughly increase this year, according to AAA, compared to last year, when the pandemic’s devastating spread discouraged flights and tourism. This month, an estimated 109 million Americans are scheduled to travel by airline, car, or other mode of transportation.

Following the December travel plans of millions of people, the omicron form swiftly grew to account for roughly three-quarters of COVID cases, prompting new pandemic measures like travel bans around the world.