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 do not 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.
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.
More than 3,000 incoming flights alone were canceled or diverted while Denver International was shut down for 45 hours after the storm hit Wednesday.
Some passengers left for hotels or gave up and went home, but others stuck it out at the airport. An estimated 4,700 camped out there at the peak of the closure.
Runways started reopening at midday Friday, and the last of the six runways reopened Saturday, giving the airport more capacity than airlines needed, Snyder said.
The troubles at Denver backed up flights around the country heading into one of the busiest travel times of the year. About 9 million Americans planned to take to the air during the nine-day Christmas-to-New Year's period, according to AAA.
Associated Press writers Judith Kohler in Denver and Sophia Tareen in Chicago contributed to this report.