(CNN) — A “technology issue” that prompted United Airlines to ground flights across the US on Wednesday, triggering more than 1,000 delays and dozens of cancellations, has been resolved, the airline told CNN.

The outage, which began at 6:12 p.m. ET and was resolved within a few hours, stemmed from an issue with the airline’s weight and balance computer system, known as Unimatic, and was unrelated to recent cybersecurity concerns in the industry, the company said. It’s not clear what caused the problem.

“The underlying technology issue has been resolved and while we expect residual delays, our team is working to restore our normal operations,” a United Airlines spokesperson told CNN on Wednesday night.

According to flight data tracker FlightAware, more than 1,000 flights had been delayed

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