Denver ? Hundreds of flights left Denver’s beleaguered airport on Christmas Eve with many passengers who had been stranded when a two-day blizzard shut down the runways last week.

The airport’s two biggest airlines, United and Frontier, said they flew full schedules of a combined 1,200 flights Sunday. They had a similar schedule Saturday as travelers around the country whose itineraries were wrecked by the storm raced to get home.

Last Christmas Eve, an estimated 129,000 passengers passed through the airport, the nation’s fifth-busiest annually, but officials say patterns change from year to year.

Airline officials said they had no way of knowing when the backlog of passengers might be cleared because they don’t know what decisions the travelers made.

“Did they cancel? Did they find another form of transportation to get to their destination? Did they book at another time?” said Frontier spokesman Joe Hodas.

United also was running nearly on schedule Sunday despite adding the 12 flights to its regular 900 and holding some planes to make sure every seat was filled, spokeswoman Robin Urbanski said.

She said many standby passengers were boarding the planes but did not know how many.

Leigh Bingham of Denver was waiting to board a flight to Albuquerque, N.M., on Sunday to spend Christmas with her parents and siblings. She said she missed a flight Friday after three hours in the airport’s security checkpoint line.

“That was the longest line I’ve ever seen, including for roller coasters,” she said.

On Sunday, the snaking line was gone and she made it through the checkpoint with plenty of time to spare.

“I’m very, very, very happy,” she said.