FAA Ground Stop Traced to Overloaded 1980s-Era Routers

The Federal Aviation Administration ordered every departing flight at every U.S. airport held on the ground Friday afternoon, effective 3:54 p.m. ET — only the second nationwide departure ground stop since Sept. 11, 2001.

The FAA's Air Traffic Control System Command Center (Advisory 111) lists the stop as ordered "due to extraordinary circumstances and for reasons of safety," with departures held "until further notice" and the advisory window running to 11:30 p.m. ET. At the time of the order, the FAA hadn't publicly confirmed a cause.

Transportation Secretary Sean Duffy said on X at 4:16 p.m. ET that a communication issue is impacting all Air Route Traffic Control Centers and that technicians are investigating. Reports put the start of the failure around 3:30 p.m. ET near the Kansas City center, with frequency problems reported across the national airspace system, and Flightradar24 ties the outage to an equipment and radio failure.

Flights already in the air may still land — about 3,100 aircraft were airborne bound for U.S. airports as of 4:19 p.m. ET, according to Flightradar24 — and inbound international flights are being handled case by case.

As of 4:26 p.m. ET, the FAA's national airspace status page no longer listed a nationwide stop, though airport-specific ground stops remained in place, including at Chicago. The agency formally announced the cancellation on its website that evening.

Update, 8:15 p.m. ET: The FAA lifted the nationwide ground stop at about 8:15 p.m. ET on Friday, November 13, and departures have resumed, the Associated Press reported. The stop lasted more than four hours from the 3:54 p.m. ET order. It was the first nationwide departure halt since January 2023, and only the second since the aftermath of the September 11, 2001, attacks.

Transportation Secretary Sean Duffy said the failure began at 3:36 p.m. ET with instability in radar and communications, when switches and routers were overloaded with data and began returning inconsistent readings, and he later tied it to old legacy equipment. The bill lands across the weekend: FlightAware counted nearly 5,000 cancellations on Friday, with about 800 more already listed for Saturday, and the analytics firm Cirium counted at least 827 diverted flights. Airlines are resetting crews and aircraft that ended the day out of position, and Delta issued a travel waiver for Friday and Saturday.

The cause, as the FAA's leadership tells it, is the age of the network itself. Transportation Secretary Sean Duffy told reporters at the White House on Friday evening that switches and routers on the agency's analog air traffic control system became overloaded with data and began returning inconsistencies in communication with airlines — and the agency shut the system down rather than trust bad data.

Duffy named the technology underneath: TDM — time-division multiplexing — a dated, mostly copper-wire system still used to transmit air traffic control voice and radar data. “We have old, old switches, old routers, we use 1980s little copper lines,” he said. “It's an old system that went down and went down everywhere.”

The breakdown produced intermittent communication and radar — not a complete blackout, Duffy said — and some channels stayed up. “We were able to keep some of those communications going, but when you have issues and you can't immediately communicate and immediately see where aircraft are at — that's a risk that we're unwilling to tolerate,” he said.

By Friday evening the FAA had deployed fixes to reduce the overloading, bringing towers and the terminal radar facilities known as TRACONs back online, and Duffy said controllers would move as many flights as Friday night allowed — a pace set less by the network than by the availability of flight crews and pilots after hours of disruption.

Both secretaries ruled out the darkest explanation, with a caveat. Duffy said there was no evidence of a cyberattack or foreign involvement, and Homeland Security Secretary Markwayne Mullin said the same — while adding that investigators haven't ruled anything out and the review continues.

Why the old system overloaded on this particular Friday isn't settled. Mullin said the failure came as the FAA was performing upgrades: “That new equipment, new technology — it was overwhelming the older system. The patchwork doesn't work. We need one complete system.” Duffy said the disruption was not directly tied to the FAA's new SMART traffic-management system, which the agency had expanded nationwide days earlier. Mullin has since sharpened that account, saying the rebuild itself overloaded the aging network — that the new equipment going in was overwhelming the system it is meant to replace. No formal cause has been determined, and CBS News has reported, citing sources, that a network update forced a reboot and a crash — an account that doesn't match the overload explanation. TML's full analysis of the two accounts is linked in the sources below.

The remedy now has numbers on it. Duffy said $12.5 billion for the upgrade is already secured through the administration's spending law, and he called on Congress to approve $50 billion more to finish modernizing the system. “None of your networks run on 1980 technology,” he told reporters. “You have all got fiber, state-of-the-art, high-speed networks — but not the FAA.”

The human bill is still being counted. More than 3,500 airplanes were in the air when the stop was ordered; tens of thousands of travelers were stranded, FEMA was mobilized so passengers didn't miss lifesaving medication, and some college football teams scrambled for ground transportation to reach this weekend's games. Airlines spent Saturday working through the backlog, and Duffy warned the cleanup would run for days.