Many United Airlines travelers found their planes grounded in the U.S. last night due to a computer glitch that kept all the carrier’s domestic flights from flying for about an hour. As is often the case in these situations, a lot of those people were pretty annoyed by the disruption.

United ordered a “ground halt” last night that was disclosed in a Tweet at 8:06 ET last night.

“A ground stop is in place for domestic flights due to an IT issue. We’re working on a resolution. We apologize for the inconvenience,” the carrier said.

In an update about an hour later, United said planes could take off again.

“The ground stop has been lifted. We’re working to get flights on their way,” United said in an update about an hour later.

The Federal Aviation Administration says international flights weren’t affected, reports Reuters, but it’s unclear how many total flights in the U.S. were included in the mass grounding. United said it would waive change fees for those affected by the IT issue.

But that wasn’t enough for many passengers, who expressed their annoyance at the airline online.

United was kept busy responding to delayed and frustrated customers, replying on social media to individual passengers in some cases.

“We are working as quickly as possible to resolve this issue and get out customers to their final destinations,” a company spokeswoman said in a statement last night.

This isn’t the first time United passengers were left stranded and delayed for hours: in June, United’s flight plan briefly lost functionality. A month later, the airline’s flights were disrupted when a glitch blocked access to reservation records. Then in October, a computer glitch halted United flights, causing system-wide delays for travelers around the globe.

United isn’t alone in its glitchiness, either, as both Delta Air Lines and Southwest Airlines suffered major technical setbacks last year that prompted delays for thousands of travelers.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.