On a Friday afternoon in mid-November, the skies over the United States fell silent for longer than anyone in the aviation system had seen since the morning of 11 September 2001. The Federal Aviation Administration halted every departure across the country after a communications failure reached all of its air traffic control centres, and thousands of aircraft were left to land, divert, or wait. Officials point to an ageing network of switches and routers, strained beyond what it was built to carry once newer equipment was grafted onto it, and they have set aside any suggestion of sabotage. It
What we know about the longest US nationwide flight ground stop since 9/11
Tens of thousands of travellers were stranded in airports across the country, many without knowing where they would sleep that night, per Transportation Secretary Sean Duffy.
"It's going to continue to fail," the transportation secretary said of the system
Mark
Why is this being compared to 9/11 at all?
Mimi
Because nothing nationwide in the US has stopped flights this long since then. It lasted over four hours, and Dr Gratton called it the worst since 9/11 but not on that scale.
Mark
What do officials say actually broke?
Mimi
Transportation Secretary Duffy says an old analogue communications system got overloaded. Switches and routers took on too much data and went down, hitting communications and radar.
Luke
That's his account. The reporting doesn't include an independent technical review, so the cause is attributed, not verified.
Mark
And the cyber-attack question?
Mimi
Homeland Security Secretary Mullin said there was zero evidence of one, and he ruled out a link to Thursday's Microsoft outage.
Luke
Worth noting the wording: no evidence found is not the same as proven impossible. It's early, though, and both secretaries were consistent.
Mark
Mullin also mentioned new technology. What does that add?
Mimi
He said new technology introduced into the old system overwhelmed it. It suggests the problem was the mix of old and new rather than one piece failing alone.
Luke
Nothing here says what that new technology was. That's still unknown.
Mark
What about the $50 billion figure?
Luke
That's Duffy's estimate, nothing more. No breakdown or timeline was given, so treat it as a rough marker.
El Pulso
- Every departure in the United States was frozen at once, leaving more than 3,500 aircraft already airborne to find somewhere to land.
- Some 8,000 flights were cancelled and 8,500 more delayed, and tens of thousands of travellers were stranded without a known place to sleep.
- Officials are ruling out a cyber-attack and a link to the Microsoft outage, pinning the failure on overloaded legacy switches and radar communications.
- Transportation Secretary Sean Duffy warns that the disruption will ripple for days and that the system will keep failing until a roughly $50 billion overhaul is undertaken.
- Airlines are restarting unevenly, with Delta and United returning while JetBlue waits until Saturday morning, and the backlog remains the immediate test.
On a Friday afternoon in mid-November, the skies over the United States fell silent for longer than anyone in the aviation system had seen since the morning of 11 September 2001. The Federal Aviation Administration halted every departure across the country after a communications failure reached all of its air traffic control centres, and thousands of aircraft were left to land, divert, or wait. Officials point to an ageing network of switches and routers, strained beyond what it was built to carry once newer equipment was grafted onto it, and they have set aside any suggestion of sabotage. It is a reminder that the invisible infrastructure carrying a nation's travel is only as sturdy as its oldest layers.
At 15:54 Eastern time on Friday, the Federal Aviation Administration announced that every flight departing within the United States was grounded until further notice. More than 3,500 aircraft were already in the air, and some were diverted while others pressed on to their destinations. The agency cited "extraordinary circumstances" involving a communications problem that reached all of its air traffic control centres. The stoppage ran for more than four hours, the longest nationwide ground stop since 11 September 2001, and the skies reopened only in the evening.
The effects travelled far beyond American airspace. Eurocontrol suspended US-bound traffic from its member states at the FAA's request, Sydney's largest international airport halted its US flights, and Air Canada cancelled services between the two countries. By the end of the day, about 8,500 flights had been delayed and nearly 8,000 cancelled.
At a late-night news conference, Transportation Secretary Sean Duffy blamed an overloaded legacy communications system, describing it as "analogue telecom" whose switches and routers had taken on more data than they could bear. Homeland Security Secretary Markwayne Mullin said there was "zero evidence" of a cyber-attack and no connection to the global Microsoft outage. Both insisted the public had never been in danger.
The human toll fell on travellers. Tens of thousands were stranded, many of them, in Duffy's words, "without any knowledge of where they're going to sleep tonight." He warned that the knock-on effects would take days to unwind, and that without a complete overhaul the system would continue to fail. Airlines responded at different speeds, with Delta and United resuming, American focused on flying what it could that evening, and JetBlue holding until Saturday morning.
The outage is already being measured against the 2023 Notam failure, which lasted under two hours. Friday's was far longer. What now matters is how quickly the backlog clears, and whether the call for a $50 billion rebuild of air traffic control becomes a concrete plan.
At 15:54 Eastern time on Friday, the Federal Aviation Administration announced that every flight departing within the United States was grounded until further notice. More than 3,500 aircraft were already in the air. Some were diverted to other airports, and others carried on to their destinations.
The FAA said the stoppage was due to "extraordinary circumstances" involving a communication issue that affected all of its air traffic control centres. It lasted more than four hours, making it the longest nationwide ground stop since the attacks of 11 September 2001. Some flights were allowed to leave San Francisco International airport hours into the stoppage, and the FAA reopened the skies until 20:15 Eastern time. By FlightAware's count, the disruption left more than 8,500 flights delayed and nearly 8,000 cancelled on Friday.
The effects spread beyond US airspace. Eurocontrol, which covers 42 member states including dozens of EU nations, the UK, Ukraine and Turkey, as well as Israel and Morocco, suspended all US-bound air traffic from those countries at the FAA's request, citing technical issues. Sydney, Australia's largest international airport, grounded all US-bound flights until further notice. Air Canada cancelled flights between the US and Canada.
At a news conference on Friday night, Transportation Secretary Sean Duffy said a legacy air traffic control communications system had become overloaded. "This is analogue telecom," he said, explaining that the switches and routers took on too much data and went down. He said the failure hit both communications and radar. He said the system needs a complete overhaul, which he put at about $50 billion, and warned: "It's going to continue to fail."
Homeland Security Secretary Markwayne Mullin said officials had seen "zero evidence" of a cyber-attack and ruled out any connection to the global Microsoft outage that began on Thursday. He said some new technology introduced into the old air traffic control system had overwhelmed it. Both secretaries insisted the public was never in danger.
The human cost fell on travellers. Duffy said tens of thousands of people were stranded in airports around the country, many of them "without any knowledge of where they're going to sleep tonight." He cautioned that the knock-on effects would last a few days. "It's going to take us some time to unwind what's happened this afternoon," he said.
Airlines responded unevenly. Delta Air Lines and United Airlines said they were resuming operations. American Airlines said it was focused on operating as many remaining flights as possible that evening. JetBlue said it would not resume until Saturday morning.
The event was only the second nationwide stoppage since the immediate aftermath of 9/11. Dr Guy Gratton, an associate professor of aviation at Cranfield University, told BBC Verify that it "looks like the worst since 9/11, but clearly not on that scale." He pointed to the 2023 grounding, caused by a failure of the Notice to Air Missions (Notam) system, which stopped safety notices from being published. That outage lasted 1 hour and 52 minutes, delayed about 9,500 flights and cancelled about 1,300. Friday's lasted considerably longer.
What to watch now is how quickly airlines clear the backlog over the coming days, and whether Duffy's call for a $50 billion overhaul of the air traffic control system turns into a concrete plan.
Citas Notables
It's going to take us some time to unwind what's happened this afternoon.— Transportation Secretary Sean Duffy
Officials saw zero evidence the outage was a cyber-attack.— Homeland Security Secretary Markwayne Mullin
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