Computer outage leads to flight delays throughout U.S.

Flights are being delayed at multiple locations across the United States after a computer outage at the Federal Aviation Administration.

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

Most delays were concentrated along the East Coast, but were beginning to spread west.

The agency said in an initial tweet that it was working on restoring its Notice to Air Missions System (NOTAMs).

"We are performing final validation checks and reloading the system now," the FAA said. "Operations across the National Airspace System are affected."

About 45 minutes later, the U.S. transportation agency ordered airlines to pause domestic departures until 9 a.m. 

Several flights to U.S. destinations on the departure boards of Canadian airports are showing delays of from 30 minutes to over an hour.

Toronto's Pearson Airport advised travellers with U.S. routes to check their flight status before heading to the airport.

White House Press Secretary Karine Jean-Pierre said U.S. President Joe Biden was briefed on the situation and had directed the Department of Transportation to investigate. There was no evidence at this point that the outage was caused by a cyberattack, Jean-Pierre said.

U.S. Transportation Secretary Pete Buttigieg said in a tweet that he is in touch with the FAA and monitoring the situation.

Biden addressed the FAA issue on Wednesday before leaving the White House.

"I just spoke to Buttigieg. They don't know what the cause is. But I was on the phone with him about 10 minutes," Biden said. "I told him to report directly to me when they find out. Air traffic can still land safely, just not take off right now. We don't know what the cause of it is."

Before commencing a flight, pilots are required to consult NOTAMs, which list potential adverse impacts on flights, from runway construction to the potential for icing. The system used to be telephone-based, with pilots calling dedicated flight service stations for the information, but has now moved online.

All aircraft are required to route through the system, including commercial and military flights.