Passengers saw their flight information vanish from airport screens, and thousands were stranded as United canceled 36 flights and delayed 100 worldwide.
The airline says connectivity issues caused computer outage, which began at approximately 7 p.m. Friday. United officials released a statement indicating it their system was completely back up and running, but officials released no further details.
On Saturday morning, United passengers said operations were definitely not normal at O'Hare International Airport. Although the electronic flight boards indicated that most flights are running on time, many passengers feared they wouldn't even be able to get onto their planes.
It appeared that the self-check in kiosks were not working for many travelers, including those who rebooked from Friday night and those who were originally scheduled for Saturday. Passengers said they were getting error messages from the kiosk machines, telling them their flights were not recognized, which means they have to get in line to check in. As a result, huge lines formed inside the terminals for both domestic and international flights.
And to make matters worse, passengers said there were not enough representatives to handle everyone at O'Hare.
"They don't have very many staff here. It's moving slow. A lot of people in the line for today's flights and they do have tickets, but they can't get onto their planes -- either because of who knows what is wrong with air tickets. So, it's chaos," said traveler Joel Nigg.
"I tried to get boarding passes. It says that the flight is not available, and check in with a representative, when I have been in three different lines, and the last line I'm in is right now, and there he's only two people at the counter, representatives to help us," passenger Florence Miller said.
United passengers flying the rest of the weekend have been advised to print out their boarding pass at home instead of at airport kiosks in case of continuing backlogs. By 3 a.m. Eastern time, United had announced on Twitter that things were returning to normal: "Flight status and flight rebooking are fully refreshed on united.com. Thanks again for your patience." Officials did not elaborate.
The airline's customer service line at O'Hare was only four passengers long by noon, and United was letting people with tickets for travel Saturday change them for free to alleviate the crunch.
There was no word from United on whether the problems with the kiosks were related to their network issues from Friday night.
For more information, visit United's website at www.united.com.
The Associated Press contributed to this report.