Thousands of flights have been delayed in the United States after Southwest Airlines was forced to temporarily ground all flights because of a "technical issue," reports BBC News.

Flight Aware says over 5,400 flights were delayed into or out of the U.S. April 18. More than 100 were cancelled.

"This morning Southwest Airlines experienced a technical issue with one of their internal systems," the FAA said, adding that all departures were paused at Southwest’s request while the carrier addressed the issue. "The pause has been lifted and their service has resumed," the FAA said.

It's the latest setback for the budget airline. Southwest Airlines has been under fire after "staff shortages" during the Christmas holiday season led to 16,700 flight cancellations and disrupted travel plans for two million customers.

The airline said it would work to accommodate passengers disrupted by the one-hour nationwide stoppage.