United Chief Executive Glenn Tilton and airline employees were informed of the breakdown by e-mail and voice mail within minutes of the 8 a.m. failure, United said. The FAA was notified simultaneously.
The city's Department of Aviation got a call and dispatched customer service staff to United gates at O'Hare at 9 a.m. Working with the city and the FAA, United began directing arriving domestic flights to Terminal 5.
The Unimatic service was restored at 10 a.m., United said. But the damage was done.
Although delays at O'Hare weren't terrible in the morning, they worsened during the day as the backups at other airports caused customers to miss connecting flights.
By the middle of the afternoon, only 34 percent of United's departures were on time, compared with 75 percent of flights operated by other airlines. More than half of United's 142 departing flights experienced delays of 45 minutes or longer.
At 3 p.m. about 80 people stood in line at a United customer service counter at O'Hare, looking for help.
Ann Snook of San Francisco was part of the queue, holding her 5-month-old granddaughter in one hand and a McDonald's sandwich in the other. She was not pleased.
After a two-hour wait in a plane on the tarmac in San Francisco, Snook missed a connecting flight from O'Hare to Jacksonville.
"They tell us the best we can do is 9 p.m. to Orlando," she sighed.
Adding to her irritation, United's customer service center had seven workstations, but only five United employees were there.
"Not all those computers are manned," Snook said. "I don't think they are doing their best."
At 3:17 p.m., United acknowledged in a statement that it would take a full day for it to recover.
\ Disruptions uneven
Various parts of United's global system were affected differently, with the largest disruptions coming at its hub at Denver International Airport.
Only 11 percent of United departures in Denver were reported on time by mid-afternoon, while 37 percent of arrivals touched down on schedule, according to FlightStats, a firm that tracks real-time and historical flight information.
"There were some big crowds on the B Concourse where United flights arrive and depart," said Chuck Cannon, spokesman for the Denver airport. "Except for at United, ticket-counter lines never got very long today."
Across its system, United canceled nearly 70 flights Wednesday, according to FlightStats. About 268 domestic and international flights were delayed for an average of 90 minutes.
While passengers holding United tickets faced lengthy travel delays, it was a great day to fly for people booked on other airlines.
"It's kind of like if all the Chevys couldn't get on the highway today. It made more room for everybody else," said Joseph Bellino, chief of the air traffic controllers union at O'Hare International Airport. "It was a very slow day for us."
\ Easy flying
A combination of generally good weather coast to coast and a sizable reduction in commercial flights caused by the grounding of all United planes for two hours made for open skies and no queues of planes waiting for runways.
"The volume of air traffic has been much lighter today, and I have not seen any delays at O'Hare or anywhere else due to weather," said FAA spokeswoman Elizabeth Isham Cory in Chicago.
Even some United passengers weren't complaining.
Meghan Barich, 29, was dropping off a relative for a United flight to Buenos Aires. She had heard about the delays and had been apprehensive when she got to O'Hare.
"It was easy and breezy," Barich said. "There was a short line and no delay."
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IN THE WEB EDITION\ Check flight and airport delays throughout the U.S. at chicagotribune.com/flighttracker
The airline now has three nonstop flights a day from Midway to Denver, Ted's base, and two daily nonstops to Washington Dulles.
Carrier expects to be back on track later today
Chicago has promised that its $14.7 billion plan virtually will eliminate late and canceled flights during bad weather.