US flight departures began resuming early Wednesday after an overnight outage to a key air-traffic system prompted authorities to ground planes nationwide.
The Federal Aviation Administration said normal air traffic operations were gradually returning as it lifted the ground stop shortly before 9 a.m. Eastern time. The disruption stemmed from problems with the Notice to Air Missions system, or Notam, which conveys advisory information essential for flight operations.
The dramatic system disruption is one of the most significant in recent decades for the FAA and comes after a year of tests of the nation’s air system as the return from Covid-19 stressed airlines and air-traffic operations.
Carriers including United Airlines Holdings Inc. and Southwest Airlines Co. said travelers should expect schedule changes, including delays and cancellations, even as flight operations began resuming. Flight-tracking website FlightAware showed 4,314 delays for US flights at 9:22 a.m. New York time.
The grounding potentially could affect more than 2 million passengers who are booked on 19,621 domestic flights, according to aviation data provider Cirium. That doesn’t include travelers on 1,843 international flights set to arrive in the US Wednesday.
The computer system that shares the notices to pilots, airlines and other users began developing problems late Tuesday night and had to be completely taken down in the early hours of Wednesday, said a person familiar with FAA’s actions who asked not to be identified discussing the situation as it develops. FAA technical workers have been troubleshooting the system since then, the person said.
There was no indication that the outage affected the FAA’s ability to track and guide aircraft, or that it caused any safety incidents.
President Joe Biden was briefed on the situation by Secretary of Transportation Pete Buttigieg, the White House said Wednesday in a tweet. The president ordered a full investigation, but there is “no evidence of a cyberattack at this point.”
“They don’t know what the cause is,” Biden told reporters.
By early Wednesday, passengers due to fly domestically began reporting delays on social media, and United said it would temporarily ground flights.
The biggest European airlines said they were largely unaffected by the disruptions, with flights from British Airways, Air France and Deutsche Lufthansa AG operating normally even as domestic US flights were halted, the carriers said.
Given the early hour of the disruption in the US, international flights were either still on the ground or nowhere near US air space, giving pilots more turnaround time to react.
Shares of most major US airlines were down slightly before the start of regular trading in New York.
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