A five-hour computer outage that virtually shut down United Airlines Friday night and early Saturday is a stark reminder of how dependent airlines have become on technology.
Passengers saw their flight information vanish from airport screens, and thousands were stranded as United canceled 36 flights and delayed 100 worldwide.
The airline still had no explanation Saturday afternoon for the outage. But things could have been much worse.
A blizzard in the Northeast wiped out more than 10,000 flights over three days in December and 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. On a Monday morning, the results could have been catastrophic.
"It happened as a lot of the airline was going to sleep for the night," Harteveldt said.
That doesn't mean affected travelers were happy.
"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 home.
Buffalo Niagara International Airport experienced none of the United delays, airport officials said Saturday.
Social workers Penny Nordstrom, 57, and Emily Schaefer, 42, who were trying to get home from Cancun, Mexico, to Spirit Lake, Iowa, 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 get home about midnight but hoped her travel insurance would offer some compensation.
United spokesman Charles Hobart said late Saturday afternoon that the airline didn't expect to cancel any more flights this weekend due to the computer problems, though delays might continue.
Business travelers are usually hurt less by such disruptions than people flying for vacation or personal reasons because airlines first help passengers with elite status in frequent flier programs and those who bought more-expensive, unrestricted tickets.
Jon Ryan, who had planned to fly nonstop from San Francisco to London on business Friday evening, was rebooked on partner airline Air Canada after two hours on the phone. His new itinerary: San Francisco to Toronto to Halifax, Nova Scotia, to London.
Airlines rely on computers today more than ever. Reservations and customer service are largely automated, even flight paths are increasingly computer-generated. Most passengers are asked to check-in online, at airport kiosks or via mobile phone -- not with an agent -- and paper tickets are a thing of the past.