DENVER — On Thursday, as thousands of travelers tried to get moving again at Denver International Airport, the line for those flying United Airlines dwarfed all others, snaking all over the sixth level of the main terminal.

And it sparked a question: Was it the result of waiting longer than other airlines to cancel flights as an unusual winter storm bore down on Colorado?

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By late Tuesday afternoon, as meteorologists were predicting that heavy snows and high winds would sock-in vast swaths of the state, Southwest Airlines had already cancelled 367 flights in an out of Denver – nearly 90 percent of those it operates on a typical day.

At that same time, according to flightaware.com, a private company that tracks aviation data, United Airlines had cancelled 80 flights in Denver.

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“As the weather changed and we got more information, we implemented additional cancellations,” said Erin Benson, a spokeswoman for United.

That number of cancellations ultimately climbed to about 700 flights, Benson said.

But travelers like Jarrell Denard were already at the airport, believing he would be able to get out of Denver, when his flight was cancelled.

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And then Denard got stranded in the airport, unable to leave as Pena Boulevard was shut down.

“Basically, it was nerve-wracking,” said Denard, who was trying to get home to San Antonio. “I mean being here, not able to leave, go home.”

Benson said she could not address why Southwest cancelled so many flights earlier than did United.

According to Benson, the decision to cancel flights was not “driven by any type of financial impact” and that the top priority when making those decisions is safety.

 “If we think we can get a flight out safely, we’re going to do it,” she said.

Roughly 5,000 people had ended up spending the night at DIA Wednesday, according to airport spokeswoman Alex Renteria. However, there is no way to know how many of them were United customers – or why they were stuck at the airport.

Some, Renteria said, may have flown into Denver and then been unable to leave because Pena Boulevard was closed.

Still, the line to get help from a United agent, or even to check baggage, dwarfed those of all other airlines at DIA on Thursday.

“I would have rather cancel the flights and let everybody know that they were cancelled,” said Kody Capps, who was trying to get to Hawaii. “At least you could make other arrangements. But I don’t like how United handled this whole situation this week.”

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Capps situation was different than other travelers: He said he was told his Wednesday flight had been cancelled but later learned it actually did get off the ground before the storm took hold. As a result, he found himself in the long line Thursday, hoping to get to baggage check in time to catch his new flight.

Cancellation decisions, that’s left up to the airlines in almost all cases – the only exception being times when the airport is closed.

“The weather was really warm the day before,” Renteria said. “But this bomb cyclone was known to be happening, and then airlines had to decide whether to fly or not.”

Benson, the United spokeswoman, said the airline cancelled more flights Thursday but expected to begin the return to normal operations in the afternoon.

United waived change fees and fare differences for affected passengers who had tickets to travel Wednesday or Thursday through select airports, including Denver. In addition, the airline was holding planes for passengers when it could.

Benson said she understood that people who couldn’t get where they wanted to go were upset.

“When it comes to travel, it’s fair that people are frustrated when there are delays,” Benson said.

And even Southwest was not spared criticism.

“Bad,” said Brian Stockmoe of Castle Rock, who faced the prospect of driving to Virginia for his son’s wedding because he couldn’t get another flight. “Bad since last night – you know, two cancellations, and the biggest problem I understand is the weather, but no response from the call center, and the application would not allow – the app would not allow you to re-book.”

9NEWS reporter Jon Glasgow contributed to this report.

Contact 9NEWS reporter Kevin Vaughan with tips about this or any story: kevin.vaughan@9news.com or 303-871-1862.