Meanwhile, the Postal Service was deploying an unprecedented effort across Colorado and Wyoming on Christmas Eve to try and get hundreds of thousands of blizzard-delayed packages to their destinations on time.
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 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.
Sharon Lewis Koho, 60, of Nampa, Idaho, also expected to leave Sunday after her flight to Boise was canceled Wednesday. On Saturday, she made herself at home on a cot with a blanket and a stack of books.
"Welcome to my living room," she said. "I have a bathroom, a drinking fountain," she said, motioning across the terminal. "I've just settled in."
Hodas said 75 to 80 workers from Frontier's Denver headquarters went to the airport Saturday to help any way they could. Even chief executive Jeff Potter helped check in passengers at curbside, Hodas said.
Crews moved about 4.4 million cubic yards of snow from runways, taxiways, ramps, deicing areas and roadways, airport spokesman Steve Snyder said.