FAA Ground Stop Cancellations Top 4,400 as Sources Tell CBS a Network Update Triggered the Crash

Since the FAA grounded every departing flight in the country this afternoon, the damage has grown well beyond the opening hours, and the first detailed account of what broke has surfaced.

The numbers keep climbing

As of 6:20 p.m. ET, FlightAware showed more than 2,700 flights canceled within, into or out of the U.S., with another 10,500 delayed. A later FlightAware tally put U.S.-related cancellations at 4,467 and delays at 10,079. Globally, the site counted 5,141 cancellations and 26,196 delays.

FlightAware cautions that those totals cover all disruptions and not only those caused by the ground stop.

Cirium, the aviation analytics firm, said at least 600 flights had been diverted by evening. Denver, Chicago, Los Angeles and Cleveland took on extra traffic.

UPS said its flights departing the U.S. are paused until further notice. Its flights within and between other countries are unaffected.

The FAA order itself states that all departing traffic stays grounded until further notice, and it runs through at least 11 p.m. ET. Homeland Security Secretary Markwayne Mullin said earlier there was no clear information on how long the stoppage would last.

What may have broken

An update to the private communications network that connects the air traffic control system caused it to reboot, leading to a crash and the outage, multiple sources told CBS News. The network is operated by L3Harris, which did not immediately respond to CBS's request for comment.

That account rests on anonymous sourcing, and neither the FAA nor L3Harris has confirmed it. Transportation Secretary Sean Duffy has said only that a communication issue is affecting all Air Route Traffic Control Centers and that FAA technicians are investigating.

President Trump, in a phone call relayed by Fox News correspondent Peter Doocy, said the disruption does not appear to be a cyberattack or the work of artificial intelligence. Trump said nobody is taking credit, which Doocy noted would be common after a large attack on critical infrastructure. Trump pointed instead to "a bunch of old broken stuff" that the FAA relies on.

Mullin said the same thing in plainer terms outside the White House: "This isn't another 9/11. This is a telecommunication outage." He also said officials are "not ruling out anything at this point," and when asked whether AI was involved, said: "You just can't rule out anything at this point."

The AI question

The FAA expanded a new AI tool called SMART, for Strategic Management of Airspace Routing Trajectories, a day before the stop. That timing set off speculation. Workweek writer Trung Phan posted on X that he would "guess there high probability" the grounding was related to it.

The developer, AirSpace Intelligence, says otherwise. "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," the company wrote on X. It did not explain how it reached that conclusion.

No FAA or administration official has tied the outage to SMART. Microsoft said it had no indication the ground stop is related to its own global outage this week. The National Weather Service said its radar systems were not disrupted.

Spillover into Canada

Toronto Pearson said around 5 p.m. ET that it had no scheduled flights to or from the U.S. By 7 p.m., it said flights not requiring U.S. airspace were still operating. The airport said it is adding staff in terminals and the U.S. departures area and has put a parking plan in place for aircraft.

NAV CANADA, the nonprofit that runs Canada's civil air traffic system, said its systems are "operating normally." It said Montreal, Calgary and Vancouver are among the airports using traffic management programs, and told travelers to expect delays.

Retired Delta pilot Mark Stephens told Business Insider the Canadian airports are likely preparing for U.S.-bound international flights that need to divert.

Stranded passengers

At LaGuardia, Fox News counted more than 260 cancellations and 600 delays. A Frontier passenger headed to Charlotte said she got no information beyond "just to wait," and planned to sleep in the terminal. Two Canadian travelers had a Toronto flight rebooked for Tuesday, and one of them said he had no insulin with him.

Minneapolis-St. Paul had an estimated 170 scheduled departures affected, according to Jeff Lea of the Metropolitan Airport Commission.

Robert Sumwalt, a former NTSB chair, called it "absolutely unprecedented." The only comparable stops were the days-long closure after Sept. 11, 2001, and a roughly two-hour halt in January 2023 over the NOTAM pilot-alert system.

The money question

Duffy and Office of Management and Budget Director Russell Vought sent Congress a letter yesterday requesting $30.1 billion to modernize air traffic control. They described the goal as "a resilient telecommunications backbone for air traffic controllers," along with modern hardware, software and towers.

That request came before today's outage, so it cannot be a response to it. It does put the administration's own description of the system's telecommunications weakness on the record a day before a telecommunications failure grounded the country.

What remains open is the cause. The FAA has not confirmed the network-update account, L3Harris has not commented, and the order stays in force through at least 11 p.m. ET tonight.