The first passenger flight in two days was a Frontier Airlines Airbus A-319, carrying a full load of 132 passengers to Atlanta.
Airline officials weren't offering much cheer to the thousands of still-stranded travelers, though: It could take days to clear out the backlog, and some passengers might not make it home for Christmas.
"We're asking for their patience as we work to get people where they need to be as soon as we safely can," said United Airlines spokesman Jeff Kovick.
Meanwhile in London, freezing fog began to lift at Heathrow Airport on Saturday for the first time in five days, and British Airways pledged to operate 95 percent of its scheduled flights.
But with some flight cancellations still expected and a large backlog of passengers whose reservations were canceled earlier in the week, travelers at Europe's busiest airport still braced for possible delays as they raced home for Christmas.
"I'm hoping that this is the day today when I fly," said Alessandra Torraco, an Italian living in Miami. "I've only got 10 days at home now, whereas before I'd got two weeks." Torraco, like many other frustrated travelers, had been living out of her suitcase at a nearby hotel.
Denver Runways Up And Running
More than 2,000 flights were canceled Wednesday through Friday at Denver, the nation's fifth-busiest airport, causing a ripple effect that disrupted air travel around the country just as the holiday crush began.
And it doesn't help that the same storm system that slammed Colorado is now blanketing the eastern third of the country with a massive band of clouds, rain, and high winds, causing flight delays from the Great Lakes to the Northeast, reports CBS News correspondent Bob Orr .
Many of the travelers stranded in Denver found themselves on standby Friday morning, hoping to get on another flight at a time when open airline seats are scarce because of the holiday, and even scarcer because airlines are cutting flights and reducing seats to cut financial losses, reports Orr.
Even one cancelled flight can leave stranded passengers scrambling. When you have a hammer blow, like the blizzard that buried Denver, the system simply can't cope.
"If a flight is canceled, then that next flight is 90 percent full," says aviation analyst Darryl Jenkins. "And so you can only put 10 or 15 passengers on that, so it takes nine or 10 flights to accommodate that one canceled flight."
"It's like the movie '(The) Terminal,' except it's real," said Joanna Snyder, a teacher from Jackson, Wyo., referring to the 2004 moving starring Tom Hanks as a European stranded at a U.S. airport.
Tempers flared when a few people tried to cut in line at the Frontier Airlines counter early today, and they were confronted by an angry former Marine. Airline workers managed to smooth out the confrontation.
Frontier had 65,000 bumped passengers to move system-wide, and the airline was already 90 percent booked for the holidays, Frontier spokesman Joe Hodas.
Atlanta businessman Scott Carr was one of them. While dozens of plows vainly battled the still-falling snow on the runways Thursday, Carr booked four flights on three different airlines to increase his chances of making it home for Christmas. He said he was considering driving to Kansas City to catch a flight.
"I just want to get home to see my family," Carr said as he stood in a Frontier Airlines line that wrapped around to the opposite side of the terminal. "If I have to drive, at least I'll be getting closer."
An estimated 4,700 travelers spent Wednesday night at the airport. By Thursday evening, about two-thirds of them had found hotel rooms, but others still slept on cots in the airport, in chairs or wrapped up in coats and cardboard shelters on the concourse floors.
Workers in orange vests directed the human traffic and offered blankets and what other supplies they could to the stranded travelers.
The storm, Colorado's worst since a March 2003 blizzard, brought life to a standstill for 3.8 million people along the Front Range — a 170-mile urban corridor along the eastern edge of the Rockies that includes Denver.
Some mountain areas got more than 3 feet of snow, and up to 25 inches fell in the Denver metropolitan area. Bus and train service was shut down. Police and National Guard soldiers rescued hundreds of people stuck in cars.
In Wyoming, a woman died while walking for help after her car became stuck in the snow, officials said. In Kansas, a woman was hit by a tractor-trailer on an icy road.
The Denver airport hoped to get 100 stranded aircraft off the ground within the first hour of reopening, then begin allowing carriers to arrive at a rate of about 10 per hour, said Southwest Airlines chief dispatcher Mike Tyson. His airline normally flies 32 daily flights from Denver and had to cancel 13 on Friday.
"They're going to start slowly and see how things go," Tyson said.
Foggy Picture Lifting A Bit At Heathrow
Relief was in sight for thousands of stranded travelers at London's Heathrow Airport on Friday after forecasters said the thick, freezing fog that forced flight cancellations and delays for four days should begin to lift. Most Americans heading home from London will eventually make it, as airlines are making long-haul flights a priority, reports CBS News correspondent Elizabeth Palmer. No such luck for those flying domestic. Stranded in waiting rooms — or even in chilly tents — they were being re-routed onto buses and trains.
Dry air from the south was expected to help remove the blanket of fog around Europe's busiest airport by Saturday morning, forecasters said. "While it may remain gray and misty, the key factor — visibility — should improve considerably," Meteorological Office spokesman Keith Fenwick said.
Heathrow — built on flat, grassy land and surrounded by reservoirs and canals — is particularly vulnerable to fog.
British Airways canceled 170 incoming and outgoing flights Friday, 84 of them domestic and the rest short-haul to Europe. While the airline's long-haul services were still operational, some departing passengers were expected to face delays of several hours.
Airport operator BAA warned that an immediate resumption of full services was unlikely because the cancellations had stranded jets and cabin crews across Europe.
Hundreds of flights have been canceled since the fog rolled in Tuesday, affecting an estimated 40,000 people.
BAA said it was providing a range of amenities for stranded passengers, including heated tents outside terminals with blankets, ponchos, sleeping mats, children's packs and food and drink. In one tent, a brass band played Christmas carols.
With Heathrow hotels full, some people slept in chilly terminals overnight while waiting to rebook a flight home.
"I knew that there was going to be trouble, but I've never seen anything quite like this," said Jon Davidson, 22, a student from Austin, Texas, waiting on Friday for a flight to Amsterdam.