Sydney Airport halted some flights to the United States after the US Federal Aviation Administration (FAA) imposed a rare nationwide ground stop linked to a telecommunications outage affecting air traffic control.
The FAA later lifted the order after more than four hours, but it remained unclear when flights held in Sydney would resume. The disruption caused thousands of delays and cancellations at major US airports.
A Sydney Airport spokesperson said the airport was monitoring the situation and that some US-bound services due to depart had been grounded.
“Passengers travelling to or via the United States should check with their airline for the latest information regarding their flight,” the spokesperson said.
Air traffic controllers were affected across all 22 regional control centres responsible for directing aircraft travelling between airports in the US. The FAA said technicians were investigating the communications problem.
US Transportation Secretary Sean Duffy said the outage was affecting communication systems used by air traffic controllers. International flights were initially to be handled on a case-by-case basis.
The US ground stop was the first nationwide order of its kind since January 2023, when a technical failure affected the FAA’s Pilot Notification System. The only earlier nationwide grounding cited was imposed after the September 11 attacks in 2001.
Markwayne Mullin, the US Homeland Security Secretary, said the problem appeared to be a telecommunications outage and that there was no indication it was a malicious attack.
“Everybody’s safe. There’s no reason to be concerned about your loved ones if they’re flying,” he said.
The FAA’s messages to airlines referred to impacts affecting communications frequencies and radar capabilities. More than 3,000 aircraft were already in the air and travelling towards the US when the order was issued, with those flights managed individually.
Passengers on aircraft that had already taxied to runways were expected to be removed, although no timetable was given for a full return to normal operations. The disruption was expected to continue affecting airports even after the technical problem was resolved.
The outage was separate from a global Microsoft disruption reported on Friday, according to Mr Mullin. The US National Weather Service also reported nationwide internet and communications problems, although there was no immediate indication the incidents were connected.
Investigators were also examining whether the communications failure could be linked to the FAA’s rollout of a new artificial intelligence system designed to identify problems and recommend ways to reroute aircraft. The system operates from one location near Washington and sends recommendations to air traffic control centres.
The US government has been replacing ageing air traffic control infrastructure, including copper wiring and radio systems. Mr Duffy has said a further 30 billion dollars will be needed to complete the overhaul, after Congress approved 12.5 billion dollars for the project last year.
