New York, New York - American Airlines unleashed chaos at airports across the country after a technical issue led the world's largest carrier to ground all its US flights for an hour during the busy year-end travel period.

"American Airlines reported a technical issue this morning and requested a nationwide ground stop." Bridgett Frey, assistant administrator for communications at the Federal Aviation Administration, said in a statement early Tuesday morning.

"The ground stop has now been lifted," she added.

The flight halt between 6:50 and 7:50 AM ET came on Christmas Eve, a day of extremely heavy air travel in the US and elsewhere. Flight delays and even cancelations are likely, despite the relatively short duration of the grounding.

The FAA and American Airlines have yet to describe the nature of the technical issue and why it led to a nationwide ground halt.

Social media lit up with travelers complaining about how the delay might impact their holidays or ruin their rendezvous with family.

"Heck of (a) way to start Christmas," tweeted one traveler who said the aircraft he was on returned to the gate and deplaned.

American posted replies to several travelers, urging patience and saying: "Our team is working to get everyone safely in the air soon."