American Airlines Group Inc. said it’s experiencing technical issues affecting all of its flights, disrupting operations on one of the busiest travel days of the year.

However, the air carrier lifted an hour-long ground stop of all its flights in the U.S. due to an unspecified technical issue, a notice on the U.S. aviation regulator’s website showed.

“Your safety is our utmost priority, once this is rectified, we’ll have you safely on your way to your destination,” the airline said in an initial statement on X, without providing any more details on the nature of the issue.

Some online postings said that the airline was suffering a software outage preventing it from calculating weight and balance requirements for its flights. The carrier said in a separate post that it’s working on a fix and that it has no estimated time frame of a resolution.

The Federal Aviation Administration said in an advisory statement that the carrier has grounded all flights nationwide.

American Airlines shares dropped as much as 5.5% in premarket trading. Christmas Eve is one of the busiest days of the year, with the FAA expecting about 30,000 flights on Dec 24 across all carriers.

Dallas-Fort Worth is expected to see about 4.7 million passengers travel through the airport from Dec. 20 to Jan. 7, according to a news release.

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