All of United Airlines flights were grounded Sunday because of a computer outage, the Federal Aviation Administration said.

"A ground stop is in place for domestic flights due to an IT issue," United tweeted. "We're working on a resolution. We apologize for the inconvenience."

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The ground stop was lifted after 9 p.m.

"The ground stop has been lifted," United tweeted. "We're working to get flights on their way."

The Aircraft Communications Addressing and Reporting System, or ACARS, was having issues with low bandwidth, officials told NBC News.

International flights were not affected.

This is a developing story. Check back for updates.

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Austin Walters died from an overdose in 2021 after taking a Xanax pill laced with fentanyl, his father said. A new law named after Austin and aimed at preventing deaths from fentanyl has resulted in its first convictions in Georgia, prosecutors said. (Family photo)

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