In an update around 7.20am ET (11.20pm AEDT), the FAA ordered all domestic flights to be grounded until 9am ET (1am AEDT) as they worked to fix the glitch within its NOTAMS – or Notice to Air Missions – system, which relays important information to pilots and airports.
“The FAA is still working to fully restore the Notice to Air Missions system following an outage,” they said in a statement on Twitter.
“The FAA has ordered airlines to pause all domestic departures until 9am Eastern Time to allow the agency to validate the integrity of flight and safety information”.
FlightAware, which tracks delays and cancellations, showed nearly 2,512 flights to, from and within the United States as being delayed as of 7.45am ET (11.45pm AEDT), but only 126 flights cancelled so far.
Most delays had been concentrated along the East Coast initially, but are beginning to spread west.
US President Joe Biden was also briefed on the situation, according to White House Press Secretary Karine Jean-Pierre.
The association representing US airlines, Airlines for America, says the outage is “causing significant operational delays.”
United Airlines said it has temporarily delayed all domestic flights.
American Airlines said in a statement it is “closely monitoring the situation, which impacts all airlines, and working with the FAA to minimise disruption to our operation and customers.”
The NOTAMS system that is experiencing the outage provides “critical flight safety operation information,” the airline says.
The FAA said in an initial tweet around 6.30am ET (10.30pm AEDT) that the agency was working on restoring the system, before updating travellers half an hour later to say the system was back up and running, in parts.
NOTAMs used to be available through a hotline but that was phased out with the internet.
The alerts span from mundane information about construction at airports to urgent flight restrictions or broken equipment.
Commercial airline pilots use NOTAMS for real-time information on flight hazards and restrictions.
The FAA stipulates NOTAMS are not to be relied on as a sole source of information, and so some flights may be able to satisfy safety requirements by using other data.
International flights bound for the US not impacted
The last flight out of Sydney International Airport to the US was a Hawaiian Airlines flight, which took off at 9.26pm.
While the Brisbane Qantas flight to Los Angeles appears to be taking off as scheduled.
European flights into the US appeared to be largely unaffected, with planes continuing to take off from Amsterdam and Paris despite the situation.
A Schiphol Airport spokesperson told CNN that “a workaround had been issued” and flights were still departing from Amsterdam.
No flights have been cancelled from Paris’ Charles de Gaulle airport, but delays were expected, according to the airport’s press office. Frankfurt Airport also told CNN it had not been impacted.
A London Heathrow Airport spokesperson told CNN that they were “not aware of cancelled flights and that flights to the US had left recently.”
Irish carrier Aer Lingus said services to the US continue and Dublin Airport’s website showed that its flights to Newark, Boston, Chicago and Los Angeles were running on schedule.
“Aer Lingus plan to operate all transatlantic flights as scheduled today,” the carrier said in a prepared statement.
“We will continue to monitor but we do not anticipate any disruption to our services arising from the technical issue in the United States.”