A technology issue caused a ground stop on all United Airlines flights destined for Chicago and numerous other major hubs around the U.S. Wednesday night.

According to an alert on the FAA’s website, all United Airlines flights destined for Chicago were halted at their departing airports at approximately 6:30 p.m.

As of 8:30 p.m., United flights departing from O’Hare were delayed an average of 120 minutes, according to the FAA.

Just before 9 p.m. Central time, the company said that the underlying issues had been resolved, and that they were beginning to work through the backlog of flights to get travelers moving again. A ground stop remained in effect at Chicago’s O’Hare Airport, along with airports in Newark and Denver.

“We are working with customers to get them to their destinations after a technology disruption on Wednesday evening. The underlying technology issue has been resolved, and, while we expect residual delays, our team is working to restore our normal operations,” a spokesperson said.

In a statement to NBC Chicago, the company cited a “technology issue” behind the ground stop.

“Due to a technology issue, we are holding United mainline flights at their departure airports,” the company said. Safety is our top priority, and we’ll work with our customers to get them to their destinations.”