A computer outage at the Federal Aviation Administration brought flights to a standstill across the U.S. on Wednesday, with hundreds of delays quickly cascading through the system at airports nationwide.

The FAA ordered all U.S. flights to delay departures until 9 a.m. Eastern, though airlines said they were aware of the situation and had already begun grounding flights.

At 8 a.m. Eastern, there were more than 2,500 delayed flights within, into or out of the United States, according to the flight tracking website FlightAware, exceeding the number of all delayed flights on the previous day. More than 150 have been cancelled.

Those numbers are likely to grow.

More than 21,000 flights were scheduled to take off in the U.S. today, mostly domestic trips, and about 1,840 international flights expected to fly to the U.S., according to aviation data firm Cirium.

The White House said that there is no evidence of a cyberattack, but President Joe Biden directed the Department of Transportation to investigate the cause of the disruption.

8:13 AM *Update*

Regina Airport Authority President and CEO James Bogusz said their were no localized issues in YQR.

The FAA Twitter page has said  “Normal air traffic operations are resuming gradually across the U.S. following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews. The ground stop has been lifted.”