American Airlines Group Inc. said that a technological issue with DXC Technology, a third-party vendor that maintains the company’s flight-operating systems, caused a brief groundstop on all U.S. flights on Christmas Eve.

The carrier said December 24 that a network hardware-related issue has been resolved and flights have resumed. American’s flight-operating system allows for air transport to be coordinated and dispatched, it said. The delay lasted for about an hour. 

“We sincerely apologize to our customers for the inconvenience this morning,” the company said in a statement. “It’s all hands on deck as our team is working diligently to get customers where they need to go as quickly as possible.”

The airline didn’t say if it expected any delays or other knock-on effects. American Air had 3,320 domestic flights and 581 international flights scheduled for the day, according to aviation data provider Cirium.

American Airlines shares rose 0.6% at 1:39 p.m. December 24 in New York, erasing an earlier decline. DXC Technology stock fell 2.1%.

American Air had said earlier it was experiencing technical issues affecting all of its flights, disrupting operations on a day where the Federal Aviation Administration expects to see about 30,000 U.S. flights across all carriers.

Some online postings said the airline was suffering a software outage preventing it from calculating weight and balance requirements for its flights.

The incident comes after Delta Air Lines Inc. suffered a multi-day grounding in July affecting thousands of travelers due to a software glitch. And it is reminiscent of a year-end meltdown at Southwest Airlines Co. two years ago involving computer system issues.