The glitch affected the boarding pass system as well as information for the airline as to how many people would be onboard and the weight of the plane.
The computer system was back up by 10:30 Thursday morning. United Airlines said everything was back to normal by 2:00 Thursday afternoon. United brought in extra planes and employees to address the problem, but at the peak of it, hundreds of passengers had to wait in line.
The line stretched from inside O'Hare's United terminal to the sidewalk outside, and it went on and on.
"We took a cab and the cab driver says he's never seen it like this, and I just thought it was the holiday rush to get out of here," flier Christy Kyhl said.
Holiday travel is not to blame; a computer glitch is the cause of delays and cancellations. From 3 a.m. to 10:30 a.m., Check-in desks and kiosks were down as United employees were forced to check in customers manually.
"We sincerely want to apologize for any disruption this has had to our customers' travel plans. We are very pleased, however, with the mobilization of other employees to O'Hare to get our customers out and on their way as quickly as possible," United Airlines Spokesperson Cindy Szadokierski said.
Nevertheless, an apology was not enough for many, who did not know if they would make their flights. A family funeral was why Bob Bullington and his sister were anxious to get to Phoenix on time.
"We booked our flight last minute and paid big money for it. But what bothers me the most, there's no representatives from United trying to inform people how they could help them out or anything," Bullington said.
Eventually United brought in extra employees to help ease the traveling pain. By 10:30 Thursday morning, the computer system was working again, and by the afternoon Terminal 1 returned to normal, as it was filled with lucky passengers who managed to miss this morning's mess.
"I wasn't affected this time. But I'm sure they'll get me on the next time around," flier Frank Sanframonti said.
"There's a lot of anxiety now. It's not fun to travel anymore," flier Aryell Cohen said.
Several passengers spoken with said they now factor into their travel plans that something could go wrong, whether it's a computer problem or, probably more commonly, weather delays. Overall Thursday, the computer glitch caused about 100 cancellations and several delays.
United says at this point they're not sure what caused the computer glitch, but the important thing is that everything is back to normal.