US lifts longest nationwide flight ground stop since 9/11 after communications failure

The US Federal Aviation Administration has lifted the longest nationwide ground stop of flights since the terrorist attacks of 11 September 2001. The agency said Friday's stoppage, which ran for more than four hours, was caused by what it called extraordinary circumstances stemming from a communication issue affecting all air traffic control centres.

The disruption produced more than 8,500 delayed flights and nearly 8,000 cancellations on Friday, according to tracking service FlightAware. The FAA's initial announcement at 15:54 EST (20:54 GMT) ordered every flight departing within the United States to remain on the ground until further notice. More than 3,500 aircraft were airborne at the time, and while some were diverted to other airports, others continued to their destinations.

A partial easing began hours later when some flights were permitted to depart San Francisco International airport, and the FAA fully reopened US skies at 20:15 EST. Homeland Security Secretary Markwayne Mullin said there was no indication of an attack and that everybody was safe.

The stoppage reached well beyond American borders. All US-bound air traffic from Eurocontrol's 42 member states, which include dozens of EU nations along with the UK, Ukraine, Turkey, Israel and Morocco, was suspended at the FAA's request because of the technical issues, according to Eurocontrol's website. Sydney, Australia's largest international airport, grounded all US-bound flights until further notice, and Air Canada cancelled services between Canada and the United States.

Transportation Secretary Sean Duffy told a Friday night news conference that the outage would produce a ripple effect lasting a few days. "It's going to take us some time to unwind what's happened this afternoon," he said, adding that tens of thousands of people were stranded at airports across the country, many of them "without any knowledge of where they're going to sleep tonight".

Delta Air Lines and United Airlines said they were resuming operations, while American Airlines said it was "focused on operating as many remaining flights as possible this evening". JetBlue said it would restart flying on Saturday morning.

Duffy attributed the failure to an ageing air traffic control communications system that buckled under its load. "So this is analogue telecom. Our switches, our routers actually got overloaded with data and they went down," he said, explaining that both communications and radar were affected. He said the system requires a complete overhaul at an estimated cost of $50 billion and warned: "It's going to continue to fail."

Mullin told the same news conference there was "zero evidence" of a cyber-attack and ruled out any connection to the global Microsoft outage that began on Thursday. He said the introduction of new technology into an old air traffic control system had overwhelmed it. Both cabinet secretaries insisted the public was never in danger during the stoppage.

It was only the second nationwide stoppage of its kind since the immediate aftermath of the 2001 al-Qaeda plane hijackings. "This looks like the worst since 9/11, but clearly not on that scale," Dr Guy Gratton, an associate professor of aviation at Cranfield University, told BBC Verify. He pointed to a 2023 grounding caused by a failure of the Notice to Air Missions system, which prevented safety notices from being published. "That lasted 1 hour and 52 minutes, delayed about 9,500 flights and cancelled about 1,300," he said, noting that Friday's incident lasted longer.