Hundreds of flights across the United States were grounded on Wednesday morning following a technical failure in the system of the Federal Aviation Administration (FAA).
The FAA has ordered airlines to delay all domestic departures until 9 am Eastern Time to allow the agency to validate the integrity of flight and safety information.
The airlines said they had already begun grounding flights.
'The FAA is working to restore its Notice to Air Missions System. We are performing final validation checks and reloading the system now. Operations across the National Airspace System are affected,' the FAA said.
President Joe Biden has been briefed by Secretary of Transportation Pete Buttigieg on the FAA system outage.
'There is no evidence of a cyberattack at this point, but the President directed DOT to conduct a full investigation into the causes. The FAA will provide regular updates,' White House Press Secretary Karine Jean-Pierre said in a tweet.
The outage comes as a result of the failure of the Notice to Air Missions system, which alerts pilots and other personnel about airborne issues and other delays at airports across the country.
According to FlightAware, a flight tracking company, more than 1,200 flights within, into or out of the US were delayed and more than 100 were cancelled.
Transportation Secretary Buttigieg said that he is in touch with the FAA and monitoring the situation.
'I have been in touch with FAA this morning about an outage affecting a key system for providing safety information to pilots. FAA is working to resolve this issue swiftly and safely so that air traffic can resume normal operations, and will continue to provide updates,' he said in a tweet.
The FAA is still working to fully restore the Notice to Air Missions system following an outage.
'While some functions are beginning to come back on line, National Airspace System operations remain limited,' the FAA said in another update of the evolving situation.