American Airline briefly grounded all its U.S. flights on Tuesday following a technical issue, causing widespread delays during the busy holiday travel season. The one-hour halt, which lasted from 11:50 a.m. to 12:50 p.m. GMT, affected flights nationwide on Christmas Eve—a peak travel day.

Bridgett Frey, the Federal Aviation Administration’s assistant administrator for communications, confirmed the incident in a statement: “American Airlines reported a technical issue this morning and requested a nationwide ground stop. The ground stop has now been lifted.”

While the specific nature of the issue remains unclear, both the FAA and American Airlines have yet to provide further details about the technical malfunction that prompted the unprecedented halt.

Social media was flooded with frustrated travelers voicing their concerns over delayed flights and disrupted holiday plans. One traveler tweeted, “Heck of (a) way to start Christmas,” after reporting that their plane returned to the gate and passengers were asked to deplane.

American Airlines responded to several travelers online, apologizing for the inconvenience and assuring passengers that their team was working diligently to resume operations. “Our team is working to get everyone safely in the air soon,” the airline posted in its replies.

The incident highlights the fragility of air travel systems during high-traffic periods and the ripple effects such disruptions can have on travelers eager to reunite with loved ones during the holiday season.