PITTSBURGH (KDKA) – Thousands of flights were canceled this holiday weekend, with 2,500 on Christmas Day alone.

That’s according to flight tracker, “Flight Aware.”

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Most of that, according to authorities, is because of the rapidly spreading Omicron variant.

It’s been a steady day at Pittsburgh International Airport, with holiday travelers making their way in and out of the airport.

For the most part, there haven’t been many issues with current flights leaving on time.

However, airport authorities have advice for those planning to fly anywhere this week.

As thousands made their way to see loved ones for Christmas, canceled flights and delays added unexpected stress.

“Arrived here at the airport this morning around 8:30 for a 10:00 flight,” said Julie Beilfuss. “While standing in the long line for TSA, got a message that my flight was canceled.”

According to Flight Aware, nearly 2,000 flights were grounded in the U.S. alone.

“I think everyone’s going to end up sleeping it who didn’t wasn’t able to get a rental car,” said Heather Thayer. “They’re all sleeping at the airport tonight.”

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The main cause behind it, authorities say, was a combination of airline crews calling out sick and the Omicron variant.

Meanwhile, in Pittsburgh, things were running smoothly.

“Travel was very smooth, we didn’t face any delays, the flight was on time,” said one traveler.

Pittsburgh International Airport patrons said so far, so good.

“It was a nice, smooth flight,” said Thomas Wynn. “It didn’t take that long. 40-minute flight. Everything was good for me.”

They said while airports were busy, they got to their destinations on time and as planned.

As for those with flights later this week, a spokesperson for the Pittsburgh International Airport says holiday travel will stay steady throughout the new year.

“We expect about 25,000 people per day arriving and departing here at Pittsburgh International now through the week after New Year,” said Bob Kerlik. “The busiest days we’ll see [are] December 23-January 2.”

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Sunday morning is expected to be another busy travel day, so make sure to get to the airport early and have patience.