June 18, 2011 -- United Airlines passengers could experience delays today and for the rest of the weekend after a computer glitch grounded planes nationwide Friday night, officials said.
Flights were delayed for hours or canceled altogether, which stranded thousands of passengers. Some travelers spent the night at the airport as they waited for the system to be restored.
Airline officials said the computer issue began at about 7:15 p.m. central time.
Officials said the issue was fixed about midnight and blamed a "network connectivity" issue for knocking out its computers for at least five hours.
"While we will be experiencing some residual effect on our flight operations throughout the weekend, United is committed to restoring normal operations as soon as possible," said Alexandria Marren, senior vice president of system operations control for United, in a statement.
The carrier apologized for the disruption and rebooked passengers.
The system outage affected many major airports, including Chicago, Los Angeles, San Francisco and Denver, where long lines of passengers could be seen.
The problem disrupted flights for some 3,000 passengers at Los Angeles International Airport alone.
"They weren't allowing anyone in. Not issuing boarding passes so we've been in this line for hours," said Linda Hulne, who was among those who were stuck in long lines.
Passenger Ron Schaffer, who was heading to Grand Junction, Colo., from Denver, said hundreds of kiosks were closed.
"Workers were trying to answer questions. They have no ability to do anything manually. They can't check baggage. You can't get baggage. You are really stuck," Schaffer told The Associated Press.
ABC News Radio and The Associated Press contributed to this report.