A disruption to a system housing United Airlines' flight information that delayed more than 1,000 flights and caused hundreds of flights to be canceled has been resolved, but travel disruptions continued into Thursday across the U.S.
The impacted system, called Unimatic, houses flight information that is fed to other systems including those that calculate weight and balance and track flight times, according to United. It’s not clear what caused the problem, which was resolved late Wednesday. While residual delays were expected, United said its team was working to restore normal operations.
“Safety is our top priority, and we’ll work with our customers to get them to their destinations,” the Chicago-based airline said in an emailed statement.
Jenny Billman said she and her husband were supposed to arrive back in Texas from a family vacation at 6:30 p.m. local time Wednesday. They didn't land in Dallas until around 10:30 a.m. Thursday, 16 hours after their scheduled arrival time.
She said they learned about the outage after already boarding their plane in Denver. They were on it for four hours before eventually getting off, and she said it became so hot in the plane that a child began to vomit repeatedly.
By 11 p.m., she said the airline called it and told passengers they had set up cots for them, but Billman said they got little sleep “because the entire time, there are announcements and they don’t turn out the lights.”
The communication breakdown was frustrating, she said.
“I think it would have gone a really long way if a desk worker would say, ‘I’m really sorry you guys are going through this.’”
About 35% of all the airline’s flights on Wednesday were delayed and 7% — 218 flights — were canceled, according to FlightAware, a website that tracks flight disruptions.
By Thursday afternoon local Chicago time, 11% of United flights for the day were delayed and 5% were canceled. Around the same time, FlightAware reported 42 cancellations at Chicago O’Hare International Airport. All but one were United flights.
United's travel alert page noted flights to or from more than a dozen U.S. airports could be affected still on Thursday. That includes airports in Denver, Newark, Washington, Houston, New York, Los Angeles, Orlando, San Francisco, Honolulu and Guam, as well as some in Europe, such as London, Frankfurt and Munich. It was an improvement from earlier in the day, when the alert page said flights through Sunday might be impacted.
The system outage, as the company described it, lasted several hours Wednesday night, United said. It wasn’t related to recent concerns about airline industry cybersecurity. United also apologized on social media to its customers and said it would pay for expenses such as hotels in some cases.
An alert on the Federal Aviation Administration website Wednesday said all United flights destined for Chicago were halted at their departing airports. Flights to United hubs at Denver, Newark, Houston and San Francisco airports also were affected.
The FAA said in a statement Thursday that it was in close contact with United and offering its support to help address their flight backlog.
Associated Press journalists Sarah Brumfield and Rio Yamat contributed.
Passengers seeks updates on their delayed flight at Louis Armstrong New Orleans International Airport, Wednesday, Aug. 6, 2025, in Kenner, La. (AP Photo/Jack Brooks)
FILE - A United Airlines jet begins to taxi at O'Hara International Airport in Chicago, May 29, 2025. (AP Photo/Gene J. Puskar, File)
