Flights across the United States were grounded Wednesday morning after the Federal Aviation Administration said it experienced a computer outage.

All flights in the U.S. were grounded following the incident, a source with knowledge of the situation. The FAA said later Wednesday morning it had ordered all airlines to pause domestic departures until 9 a.m. ET.

More than 2,500 flights within, into and out of the U.S. were delayed as of around 8 a.m. Wednesday morning, according to online flight tracker FlightAware. Nearly 250 flights were listed as cancelled.

The FAA had said in a notice on its website that its Notice to Air Missions (NOTAM) system had “failed.” A NOTAM is a notice containing information essential to workers involved in flight operations.

"Operations across the National Airspace System are affected," the FAA said in a statement.

In an update posted to Twitter just before 7:20 a.m., the FAA said it had ordered airlines to pause all domestic departures until 9 a.m. ET "to allow the agency to validate the integrity of flight and safety information."

It said it was still working to fully restore the NOTAM system following the outage.