BY SCOTT MAYEROWITZ
AND BARBARA RODRIGUEZ
The Associated Press
CHICAGO -- A five-hour computer outage virtually shut down United Airlines Friday night and early Saturday.
Passengers saw their flight information vanish from airport screens, and thousands were stranded, though United canceled a relatively few 31 flights and delayed 105 worldwide.
The airline still had no explanation for the outage by Saturday afternoon, after normal operations had resumed. But things could have been much worse.
A blizzard in the Northeast wiped out more than 10,000 flights over three days in December, a mid-January storm led airlines to cancel nearly 9,000 flights.
Friday's shutdown occurred late enough in the day that many of the canceled flights were the last planes out for the day, said Henry Harteveldt, an airline analyst with Forrester Research.
"It happened as a lot of the airline was going to sleep for the night," he said.
That wasn't much solace for affected travelers.
"I'm just amazed at how catastrophic the failure was," said Jason Huggins, 35, who was trying to fly home to Chicago after a week working at his software company's San Francisco headquarters. "All the computer screens were blank, just showing the United logo."
Huggins paid $1,200 to book one of the last three seats left on an American Airlines flight instead.
Computer glitches are "infrequent, but the fact that they happen at all is puzzling. These are mission-critical," said airline analyst Robert Mann. "The idea that they would fail is troubling."
Mary Clark, a United spokeswoman, said she couldn't say how many passengers were delayed.
About the outage itself, she and other airline personnel said only that it was caused by "a network connectivity issue."
Social workers Penny Nordstrom, 57, and Emily Schaefer, 42, who were trying to return from Cancun, Mexico, to Spirit Lake, Idaho, said their delays started with a computer problem at midday Friday in Mexico.
"We're way past 24 hours now," Nordstrom said about noon Saturday before she boarded a rebooked flight from Chicago O'Hare International Airport to Detroit for a connection to Sioux Falls. She expected to be home about midnight and hoped her travel insurance would offer some compensation.
On a typical day, United, a subsidiary of United Continental Holdings Inc., cancels 15 to 30 flights for reasons ranging from fog to maintenance problems or staffing shortages.