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Cause of chaos revealed as flights resume after nationwide FAA grounding leaves thousands stranded
The cause of the chaos that grounded flights across the US for nearly five hours on Friday has been revealed, as departures resume following the nationwide shutdown.
The Federal Aviation Administration (FAA) suspended departing flights across the country following a communications failure affecting air traffic control systems.
According to the Wall Street Journal, more than 13,000 flights were delayed or canceled during the disruption, with officials warning that the effects could take days to resolve.
The Trump administration has identified the outage's apparent cause, blaming a software update that overwhelmed parts of the country's "incredibly old" air traffic control system.
Officials reveal what caused the disruption
The FAA confirmed on Friday evening that the ground stop had been lifted, allowing flights to begin departing again.
"So at 8.15 tonight, Eastern Time, we’ve opened up the airspace," Sean Duffy, the US transportation secretary, said. "But it’s going to take us some time to unwind what happened this afternoon."
Duffy confirmed that officials had "identified the problem" responsible for the disruption, and that the system "is operational right now".
The trouble began around 3:36PM, when air traffic control centers experienced instability affecting radar and communications systems.
Speaking at a White House briefing on Friday evening, Duffy said, "What we have is an incredibly old air traffic control system. Our routers actually got overloaded with data, and… they started to give us inconsistency in the data from those routers. And because of that, we shut the system down."
The resulting instability affected communications between pilots and controllers, as well as access to radar information.
Duffy used the incident to renew calls for Congress to provide funding to replace the aging infrastructure, urging lawmakers to "fully fund a full build of a brand new air traffic control system".
Homeland Security Secretary Markwayne Mullin, who was at the briefing, said preliminary findings did not suggest the outage was caused by a deliberate attack.
"There’s no indication as of yet that this was a nefarious attack against it. It’s just a telecommunications outage as of right now," he told reporters.
President Donald Trump also told Fox News he didn’t believe it was a cyberattack, attributing the failure to infrastructure that relied on "some old broken stuff".
More than 13,000 flights disrupted as delays continue
More than 13,000 flights were delayed or canceled as a result of the incident.
Officials have warned that restoring normal schedules could take several days, even after the ground stop was lifted.
Some flights were later cleared to depart, including planes leaving San Francisco for Hawaii and destinations in Asia.
However, Duffy could not guarantee that a similar outage would not happen again.
When he was asked whether the problem could recur, he replied: "I don’t know."
Officials deny new AI technology caused the outage
The disruption came just days after the FAA introduced a cloud-based AI system known as Strategic Management of Airspace, Routes, and Trajectories (SMART) on November 10
The timing raised questions about whether the technology could have led to the communications failure, but Duffy denied it.
Friday's disruption was the third nationwide grounding of departing flights in US aviation history.
The first happened on September 11, 2001, following the terrorist attacks, when authorities ordered an unprecedented shutdown of American airspace.
The second took place in January 2023, when the FAA temporarily halted domestic departures after a malfunction in its Notice to Air Missions system, which provides pilots with critical safety information.
FAA shared that more than 14,000 air traffic controllers oversee approximately 44,000 flights operating across the US each day.