FAA Lifts Nationwide Ground Stop After US Flights Halted

Key takeaways: The US Federal Aviation Administration halted all departing flights nationwide for more than four hours on Friday after a communications failure hit air traffic control centres. More than 1,000 flights were cancelled and nearly 10,000 delayed. Officials say overloaded switches and routers on the ageing system caused the outage, and there is no evidence of a cyberattack.

Flat illustration of an airport air traffic control tower with a glowing radar dish and passenger airplanes parked on the tarmac at dusk, in deep navy, teal and gold tones — Illustration: WHAT TODAY?

The United States grounded every departing flight in the country for more than four hours on Friday after a communications failure struck its air traffic control system, stranding hundreds of thousands of passengers in the most serious nationwide aviation shutdown in almost four years.

The Federal Aviation Administration, the FAA, issued the nationwide ground stop at 3:54 p.m. Eastern Time on Friday, November 13, citing what it called “extraordinary circumstances and reasons of safety”. Planes already in the air were allowed to land, but nothing on the ground could take off. International flights were handled on a case by case basis, the agency said.

The stop was lifted at 8:15 p.m. Eastern Time, and airlines began moving aircraft again within the hour. Delta Air Lines and Southwest Airlines both said they were safely resuming operations, although officials warned it would take time for schedules to return to normal after thousands of flights were disrupted.

What happened

The sequence began in the early afternoon, when the FAA started detecting instability in radar and communications systems at its air traffic control centres. Transportation Secretary Sean Duffy said the first signs of trouble appeared at 3:36 p.m. Eastern Time, less than 20 minutes before the ground stop was ordered.

“The FAA issued a nationwide ground stop for all U.S. airports following a communication issue impacting all Air Route Traffic Control Centers. FAA technicians are investigating the issue. We will provide immediate updates as we have them,” Duffy said in a statement.

The order covered all 22 of the FAA’s air route traffic control centres, the regional facilities that guide aircraft between airports across the country. In a post on the social platform X, the FAA described the problem as a temporary telecommunications outage and said that, as a precaution, all flights were being halted.

“Every flight has been accounted for and international flights will be handled on a case by case basis,” the agency said.

Exceptions were made for critical flights. Duffy said medevac flights, life-saving cargo and law enforcement flights were allowed to continue operating during the stoppage.

At airports across the country, departure boards turned red and travellers scrambled for alternatives, with many trying to reach their destinations by rental car, train or bus. The disruption also reached college American football, with teams travelling to Saturday games caught up in the cancellations and delays.

What caused the outage

Duffy later attributed the outage to the FAA’s legacy network, saying switches and routers in the system had become overloaded with data and went down. The system is built on analog technology that in some places dates back to the 1980s, and Duffy described it as incredibly old.

“What we have is an incredibly old air traffic control system,” he told reporters at the White House, adding that the overloaded equipment had started sending inconsistent data from the routers, which led officials to shut the system down.

He was careful to say the failure was not a total collapse. The FAA did not lose all radar or telecommunications capability, and the outage did not involve a complete loss of communications with aircraft in the air.

The precise trigger for the overload has not yet been determined. Bloomberg reported, citing an official familiar with the matter, that investigators were examining whether a software update could have caused the outage. Homeland Security Secretary Markwayne Mullin suggested that new technology being introduced into the old system may have overwhelmed it, saying that as patches and new technology were being put in, the new technology was overwhelming the system.

Officials also moved to clear one piece of new technology of blame. Air Space Intelligence, the company behind the FAA’s AI-powered air traffic management system known as SMART, said its technology was not responsible for the ground stop. Duffy said the disruption was not directly tied to the SMART system.

No sign of a cyberattack

Within hours of the shutdown, senior officials moved to rule out a hostile act, a point they repeated through the evening as speculation spread online.

Mullin told reporters outside the White House that there was no evidence the outage was caused by a cyberattack or any other nefarious act, and he sought to reassure the public directly.

“Everybody’s safe. The flights are accounted for,” he said. “This is not another 9/11.”

The FBI does not believe a cyberattack or criminal activity caused the failure, Bloomberg reported, citing an official familiar with the matter. Mullin said President Donald Trump had declared the air traffic control failures a national emergency.

Officials also ruled out any connection to the global Microsoft outage that disrupted Outlook and Teams services in 74 countries earlier in the week. Mullin said there was no link between the two events, and Microsoft said it had no indication that the flight stoppage was related to any of its services.

The scale of the disruption

The numbers show how quickly a single failure can cascade through the busiest aviation system in the world. Airlines cancelled more than 1,000 flights and delayed nearly 10,000, according to flight-tracking service FlightAware, with about 9,500 flights delayed or cancelled in total on the day.

The timing made the disruption worse. More than 1.5 million passengers were scheduled to depart US airports on roughly 11,000 flights after 4 p.m. Eastern Time, shortly after the ground stop began, according to aviation analytics firm Cirium. Many of those passengers were heading into the weekend, and the backlog of cancelled and delayed flights is expected to affect schedules into Saturday.

The halt was the first nationwide ground stop since January 2023, when a failure in the FAA system that distributes critical safety notices to pilots stopped departures across the country. It was only the third nationwide ground stop in American aviation history.

For readers in Pakistan, the story drew unusual attention. “US flights grounded” was the top trending Google search in Pakistan on Saturday morning, and travellers with US connections, including those routing through Gulf and European hubs, were among those checking flight status. Air India, which flies between India and the United States, issued a travel advisory warning passengers of possible disruptions.

An ageing system under strain

The shutdown has renewed scrutiny of the state of the American air traffic control network, which has been beset for years by equipment failures, communications problems and shortages of controllers while the FAA tries to replace ageing infrastructure.

In September, FAA Administrator Bryan Bedford told Reuters that the agency’s more than 300 air traffic facilities operated as technological silos, relying in some cases on decades-old computers and telecommunications systems that cannot communicate seamlessly with one another.

Reuters, which reviewed the biggest disruptions of the past three years, found that communications equipment problems have become an increasingly common cause of delays and cancellations, even when they do not lead to a nationwide shutdown. Friday’s halt was different only in scale: the same kind of failure, hitting every control centre at once.

The Trump administration has made modernising the system a priority, and Duffy and his team have been introducing new technology across the network over the past year. Friday’s events will sharpen the debate over whether that modernisation is moving fast enough, and whether new systems can be installed without destabilising the old ones they are meant to replace.

What happens next

The FAA said its technicians were investigating the outage and promised immediate updates as more information became available. The investigation will need to establish exactly what overloaded the switches and routers, and whether a software update or another change played a part.

For travellers, the advice is straightforward: check with the airline before heading to the airport, and expect knock-on delays while airlines work through the backlog of cancelled flights and reposition aircraft and crews. Airlines have begun rebooking affected passengers, but with so many flights disrupted in a single afternoon, some journeys will take a day or more to recover.

The wider question is what the shutdown means for confidence in the system. A nationwide ground stop is one of the most drastic steps the FAA can take, and it is used only when controllers cannot be sure they can keep aircraft safely separated. That it was needed at all, on a routine Friday afternoon, will keep the state of America’s air traffic control network in the spotlight long after the last delayed flight takes off.

Frequently asked questions

Q: Why were US flights grounded on November 13?
A: The FAA issued a nationwide ground stop at 3:54 p.m. Eastern Time after a telecommunications outage affected all 22 of its air route traffic control centres. Transportation Secretary Sean Duffy said switches and routers in the ageing analog system became overloaded with data and went down. The stop was lifted at 8:15 p.m. Eastern Time, more than four hours later.

Q: Was the FAA ground stop caused by a cyberattack?
A: No evidence points to a cyberattack. Homeland Security Secretary Markwayne Mullin said there was no indication of a nefarious attack, and the FBI does not believe a cyberattack or criminal activity caused the failure, according to Bloomberg. Officials also ruled out any link to the week’s global Microsoft outage. Investigators are examining whether a software update played a role.

Q: How many flights were affected?
A: Airlines cancelled more than 1,000 flights and delayed nearly 10,000, according to flight-tracking service FlightAware, with about 9,500 flights delayed or cancelled in total on the day. More than 1.5 million passengers were scheduled to depart on roughly 11,000 flights after 4 p.m. Eastern Time, according to aviation analytics firm Cirium.

Q: What should travellers do now?
A: Check flight status with the airline before travelling, as knock-on delays are expected while airlines clear the backlog and reposition aircraft and crews. Delta and Southwest said they resumed operations after the stop was lifted, but officials warned it would take time for schedules to return to full capacity.