A communications failure at all 22 US air traffic control centres forced the FAA to halt departing flights nationwide for more than four hours.
The disruption led to over 4,700 cancellations, 10,000 delays and hundreds of flight diversions, according to figures reported Friday.
US officials said there was no indication of a cyberattack, while the outage renewed scrutiny of the country's ageing air traffic control infrastructure.
The Federal Aviation Administration (FAA) lifted a nationwide ground stop on Friday, November 13, after a communications failure at air traffic control centres forced the suspension of departing flights across the country, disrupting thousands of journeys and leaving passengers stranded at airports. Although the agency allowed departures to resume after more than four hours, airlines continued to face cancellations and delays as they struggled to restore their flight schedules.
The shutdown was triggered by a telecommunications outage affecting the country's air traffic control network, which manages aircraft movements between airports. While officials said there was no indication of a cyberattack, the precise cause of the failure remained under investigation. The incident has also renewed concerns about the reliability of the US aviation system, which has been undergoing a long-delayed modernisation programme to replace ageing technology and communications infrastructure.
Reuters reported that more than 6,600 flights had been cancelled and 8,600 delayed on Friday, according to FlightRadar24. Another 1,500 cancellations had already been recorded for Sunday, November 15, as the disruption continued to affect airline schedules. The nationwide ground stop, which lasted more than four hours, was the first since January 2023 and the second since the September 11, 2001, attacks.
What Caused The Nationwide Flight Shutdown In The US?
The FAA ordered the nationwide ground stop on Friday afternoon after reporting serious communications problems affecting air traffic control centres. The disruption initially affected operations in Chicago before the agency extended the restrictions across the country.
US Transportation Secretary Sean Duffy confirmed that the problem affected all 22 Air Route Traffic Control Centres, which manage aircraft movements along flight routes. He said FAA technicians were investigating the failure and would provide updates as more information became available.
The FAA described the situation as extraordinary circumstances and said the ground stop was necessary for safety reasons. Its notice stated that all departing traffic should remain grounded until further notice. Aircraft already in the air were allowed to land, while some international departures were handled on a case-by-case basis.
The restrictions were subsequently lifted on Friday night, allowing departures to resume. However, the return to normal operations was expected to take longer because aircraft and flight crews had been left out of position across the country.
Was It A Cyberattack? What US Officials Have Said
The communications failure prompted questions about whether the disruption could have resulted from a cyberattack or interference with the country's aviation systems.
US Homeland Security Secretary Markwayne Mullin said there was no indication that the outage was caused by a deliberate attack. Asked whether investigators could rule out a cyberattack or an artificial intelligence-related incident, he said: "There's nothing completely certain right now. It doesn't appear that way."
Mullin added that investigators had found no signs of an attack and that the failure appeared to be "mechanically driven". He said officials were continuing to examine what had caused the disruption.
He also sought to reassure the public about the safety of passengers and aircraft. "This isn't another 9/11," he said.
The Associated Press (AP) reported that Mullin had also raised the possibility that the introduction of new technology into an older air traffic control system had overwhelmed some of its existing infrastructure. However, officials had not established a definitive connection between the technology rollout and the communications failure. The AI-supported system, which operates from one location near Washington, DC, sends recommendations to air traffic control centres rather than directly managing their communications systems.
Thousands Of Flights Delayed And Cancelled As Passengers Stranded
The shutdown affected airports across the US, with passengers facing cancellations, extended delays and uncertainty over their travel plans.
The impact extended beyond departing flights. According to AP, at least 827 flights had been diverted by 7:05 pm Eastern Standard Time on Friday, citing aviation analytics company Cirium. Of these, 670 were sent back to their original departure airports, while 157 were redirected to other airports.
Around 11,000 flights carrying more than 1.5 million passengers were scheduled to depart from US airports after 4 pm Eastern Standard Time on Friday, raising the possibility of further cancellations and diversions.
Passengers also faced uncertainty over their travel plans. Amber McQuilkin, who was travelling to New York, told AP: "There's not really any information being passed to me."
The disruption also affected sports teams travelling for scheduled matches and cargo operations. FedEx said it was prepared to activate contingency plans to minimise possible disruptions to its services.
Although the FAA lifted the ground stop on Friday night, airlines faced the additional challenge of repositioning aircraft and crews before they could resume normal schedules.
US Air Traffic Control System Faces Scrutiny Over Ageing Infrastructure
The nationwide disruption has renewed concerns about the condition of the US air traffic control system, which has faced equipment failures, communications problems and staffing shortages.
The government has been working to modernise the system, with Congress approving $12.5 billion for the overhaul last year. The funding was approved to modernise the country's ageing air traffic control infrastructure, including its telecommunications and radar systems.
Duffy said the outage was part of a wider problem involving outdated technology and deteriorating infrastructure at air traffic control facilities across the country. “Many of our towers are almost 100 years old,” he said, pointing to leaking roofs, broken air conditioning and non-functioning elevators.
He also highlighted the ageing communications network, saying it relied on “old switches, old routers” and “1980s little copper lines” that were overloaded.
Duffy has said another $30 billion will be needed to complete the air traffic control overhaul. Separately, the White House and Department of Transportation urged Congress to approve an additional $30.1 billion for upgrades to US airports and the air traffic control system, according to Reuters.
Asked whether the same disruption could happen again, Duffy told reporters, “Is this exact thing going to happen again?” He added, “I don’t — I don’t know that this exact scenario will happen.” Duffy also urged Congress to approve further spending to modernise the aviation system, saying, “And so I would say, America, Congress, let’s make this system more safe.”
According to AP, the government has begun replacing old copper wires with fibre-optic lines, while older radio systems are gradually being replaced at airports across the country.
Aviation safety expert Steve Arroyo, a former United Airlines pilot, told AP that the communications failure appeared similar to a regional outage in September that disrupted hundreds of flights across the northeastern US, although Friday's incident affected the country on a nationwide scale.
"If you don't have that ability, whether it's because the old wires that they have are just run down or for whatever reason, you've got to stop airplanes on the ground," Arroyo said. "And not put them in the air where you're going to risk not being able to communicate with them."
Friday's incident was the first nationwide ground stop since January 2023, when a malfunction in the FAA's Notice to Air Missions (NOTAM) system halted domestic departures for less than two hours. The previous nationwide shutdown before that followed the September 11, 2001, attacks.
While flights have resumed, the investigation into the communications failure continues. The incident has once again brought attention to the challenges of maintaining the country's ageing aviation infrastructure as authorities work to modernise the system.
