FAA lifts a nationwide ground stop after a communications outage

A communications problem hit the FAA's air traffic control centers. These are the big facilities that guide planes between airports. The FAA responded with a nationwide ground stop, an order that keeps planes from taking off. Planes already flying kept going and landed as normal.

Transportation Secretary Sean Duffy announced the stop on X, citing a "communication issue impacting all Air Route Traffic Control Centers." Departures stayed frozen for more than four hours. The stop was lifted in the evening, after 8 pm Eastern.

The damage was large. At 8:39 pm ET, FlightAware listed 5,901 US flights as cancelled and 9,124 as delayed. A later count passed 6,300 cancelled and 9,500 delayed. Air Canada cancelled all of its flights to and from the US for the evening.

The FAA has ordered a nationwide ground stop only three times. The first came after the attacks of September 11, 2001. Commercial flights did not restart until September 13.

The second was on January 11, 2023. A failure of the system that sends safety notices to pilots, called NOTAM (Notice to Air Missions), grounded flights for about 90 minutes. Friday's stop lasted far longer than that one.

• September 11, 2001: all civilian departures stopped for two days.
• January 11, 2023: about 90 minutes, caused by the pilot notice system.
• November 13, 2026: more than four hours, caused by a communications failure.

The explanation has two parts, and they fit together. Duffy said the terminal radar approach control facilities, which guide planes near airports, "started to have inconsistency in the data from the radars and the communications from airplanes."

He said the problem sat in analog telecom devices, the older switches and routers that carry the data. They "got overloaded with data" and began to show inconsistent results.

Mullin said the trouble began when "patches" were put into the system while new equipment was being installed. "The new technology was overwhelming the older system," he said. Duffy added that the outage was not something he had expected.

In real life Picture a small town's phone exchange suddenly asked to handle a big city's calls. The calls do not just slow down. Some get garbled, and the operators stop trusting what they hear.

The big picture: Duffy used the moment to argue for a full replacement of the old system.

Several reports tie the failure to the FAA Telecommunications Infrastructure, known as FTI. It is the private communications backbone for air traffic control. It carries voice and data between control centers, radars and pilots.

The contractor L3Harris Technologies manages the older system. It is being replaced as part of a multiyear project that swaps decades-old copper wire for fast fiber-optic cable. L3Harris said in May that it had finished 50 percent of its modernization work. Earlier this month it said 70 percent of FAA sites had been upgraded to fiber.

L3Harris did not respond to requests for comment on Friday. The company's own website says its team can "upgrade systems without disrupting air traffic operations."

One account says the problem began at the Chicago air traffic control center. Boston, Washington, New York and Minneapolis followed, and more facilities reported trouble after the FAA ordered the stop for planes flying east. That sequence has not been confirmed by the FAA.

The problems touched both the radar and the radio frequencies that controllers and pilots use. Without both, a controller cannot see a plane or talk to its crew. Stopping departures is the safe answer.

The catch: a ground stop stops takeoffs, but it does not put planes and crews back where they should be. Many flight crews ran out of legal working hours while waiting.

Days earlier, on November 10, the FAA switched on a cloud-based system called SMART nationwide. SMART stands for Strategic Management of Airspace, Routes and Trajectories. It uses artificial intelligence to study airline schedules, weather, airport capacity and airspace limits. Its job is to predict traffic jams before they happen.

The software comes from Air Space Intelligence (ASI). In June, the FAA gave the company a 12-year, $875 million contract to deploy it.

Asked about a link, Mullin said officials were looking into it. ASI answered quickly on X: "The current ground stop is not based on or a result of the SMART system, any product of ASI or our integration with FAA and ATC."

No evidence of a link has been shown so far. Officials also said they saw no connection to the Microsoft Outlook outage earlier this week.

Officials say no. Mullin said there was no indication of a security threat or a cyberattack. But he also said that, early on, no cause had been ruled out, and that "there's not complete certainty right now."

The FAA handled incoming international flights case by case. Mullin said flights were accounted for and that the public had no reason to fear.

Friday's outage landed in the middle of a money debate. Earlier that day, Duffy sent congressional leaders a letter asking them to approve $30.1 billion for air traffic control and airport upgrades. After the outage he raised the number: "I want $50 billion."

A September report from the Government Accountability Office (GAO), which audits federal agencies for Congress, raised concerns about the speed of the plan. It said the FAA's push to speed things up "could be prioritizing speed over costs and air traffic disruption." It also found no master schedule, but 11,389 separate schedules that are not joined up.

The government says it wants to overhaul the system by the end of 2028. In August, the FAA picked AT&T to build the replacement network, with a first contract of $73 million that could grow into the billions.

Duffy cautioned that without large system updates there will be "more of these." Last week the FAA also announced it is retiring floppy disks at more than 400 air traffic sites.

• Check your flight: crews and planes are out of place, so delays and cancellations are likely through the weekend. Use your airline's app before heading to the airport.
• Ask for a rebooking early: airlines are dealing with thousands of cancelled trips, and the first people to ask often get the first seats.
• Expect a long tail: it may take days, even weeks, to get schedules fully back to normal, especially for freight and mail.
• Watch the cause: the official explanation is early. Details could change as investigators look at the failed equipment.