United Airlines system outage disrupts flights nationwide

Aug. 6 (UPI) -- United Airlines on Wednesday night was dealing with a backlog of delayed flights because of a technology issue that grounded planes nationwide.

At 5:12 p.m. CDT, the Chicago-based airline reported an outage and asked for a ground stop for departures at airports, CBS News reported. Around 9 p.m., the system was coming back and United was attempting to get the planes back in the air.

The airline didn't explain the outage but said it wasn't related to cybersecurity concerns, CNN reported.

"Due to a technology issue, we are holding United mainline flights at their departure airports," United said in a statement obtained by ABC News. "We expect additional flight delays this evening as we work through this issue. Safety is our top priority, and we'll work with our customers to get them to their destinations."

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United later posted on Instagram: "We are working with customers to get them to their destinations after a technology disruption on Wednesday evening. The underlying technology issue has been resolved, and, while we expect residual delays, our team is working to restore our normal operations."

The airline said to go to united.com or its United app for the latest flight information.

The Federal Aviation Administration temporarily issued a ground stop for United flights at United hubs: Chicago O'Hare International Airport, Denver International Airport, Newark Liberty International Airport, Houston's George Bush International Airport and San Francisco International Airport.

By 11 p.m. EDT, all stops were canceled.

Airports urged travelers to check with the airline on status. Passengers on connecting flights with other airlines could be affected.

United Express Flights and those already in the air were not affected, the airline told ABC.

United has approximately 4,600 flights per day at 354 destinations in 38 countries.

Through 11:30 p.m. EDT Wednesday, 1,079 flights have been delayed, 35% of the flights, and 89 have been canceled, according to FlightAware.

At O'Hare, 29 flights -- 19 departures and 13 arrivals -- had been canceled. The airport was reporting delays of two hours, as of 9:30 p.m. CDT.

A line of United planes at O'Hare was stopped at the tarmac waiting for available gates, according to video taken by a passenger to CBS News.

CBS News reported because this is a preventable delay, the airline will pay for customer expenses, including hotels.

Transportation Secretary posted on X: "I've been briefed by United CEO Scott Kirby on their company's internal tech outage. The issue was specific to United's operations, and is unrelated to the broader air traffic control system.

"We've offered our full support to help them clear up the flight backlog."

Last month, outages affected several hundred flights involving American Airlines and Alaska Airlines.