By Sophie Lindqvist

Every scheduled flight in the United States was grounded on Friday, Nov. 13, 2026, after the Federal Aviation Administration ordered a national ground stop citing "extraordinary circumstances and reasons for safety."

That shutdown marks the FAA's first nationwide halt since a pilot-alert system outage in January 2023, and only the third such event since Sept. 11, 2001.

What caused the shutdown?

A communications failure inside the air traffic control network. Transportation Secretary Sean Duffy said the ground stop was ordered because of a "communication issue impacting all Air Route Traffic Control Centers" — the regional hubs that route aircraft between sectors of the national airspace.

Duffy, writing on X, added: "FAA technicians are investigating the issue." The agency itself said on Friday afternoon that it had detected a temporary telecommunications outage.

The FAA's own statement was blunt about the consequence. "Out of an abundance of caution, all flights have been halted," it said, adding that "Every flight has been accounted for and international flights will be handled on a case by case basis."

The mechanism, however, remains unstated. Transportation officials have not yet said why they issued the ground stop, and no technical explanation has been published. What the record shows so far is a symptom, a precautionary response and a still-running investigation.

What happened in the terminals?

The ground stop became a multi-hour ordeal, with passengers deplaned, asked to leave flights, and scrambling for luggage as boarding areas filled.

• JFK International, New York: passengers walked past boards showing delayed flights.
• McGhee Tyson Airport, Knoxville: waiting passengers filled the terminal after the Nov. 13 order.
• Dulles International, Virginia: security check lines grew longer, and traffic piled up outside the terminal.
• Logan International, Boston: departure boards flashed red and orange.
• Salt Lake City: queues formed after passengers were told to disembark a flight to Chicago.
• O'Hare, Chicago: aircraft parked back-to-back on the tarmac.

Jon Lett, a passenger traveling from Salt Lake City to Chicago, told Business Insider that everyone on his flight had been told to disembark and wait. He described the mood among passengers as "chill," though he had no way to judge whether the flight would depart anytime soon.

Was the new AI scheduling system to blame?

The suspicion has a commercial context worth stating plainly. In June, Duffy and FAA Administrator Bryan Bedford announced that the agency had awarded a contract to Air Space Intelligence for two technologies intended to improve how flights are scheduled and managed across the national airspace system.

The resulting system, named SMART, runs on Air Space Intelligence's National Airspace System, which uses "the AI that models the entire system, from the airline operation to air traffic control, and clears the bottlenecks before delays cascade."

Air Space Intelligence said in an X post that the new system was not the cause of the communications problem that prompted the ground stop.

That denial deserves scrutiny rather than acceptance. It comes from the vendor whose contract is exposed, and the FAA has not independently confirmed it. A system that, by its own description, models the entire national airspace is also a system whose failure modes would warrant outside examination.

How rare is a national ground stop?

National ground stops are historically rare for the FAA. The January 2023 precedent involved an outage affecting the agency's pilot alert system. Before that, nationwide air traffic was halted following the Sept. 11, 2001 terrorist attacks.

The comparison is instructive on scale rather than cause. An aging alerting system and a communication network serving every control center are different failure modes, and the frequency of the event tells us little about the reliability of either.

What does this change for airlines and passengers?

For passengers, the practical change is immediate and physical: no departures, no arrivals, and international flights handled case by case. For airlines, it is a scheduling and revenue shock absorbed through rebooking, misconnections and aircraft and crew displacement.

The numbers that would normally quantify that shock are missing. The record discloses no count of affected flights, no estimate of economic cost, no restoration timetable, and no explanation of why a telecommunications outage required halting every aircraft in the country rather than degrading service. Boarding-area photography confirms scale; it does not substitute for data.

Three things will settle the question. The FAA's technicians' findings on the communications failure; whether international flights resume under the case-by-case protocol; and whether SMART returns to the investigation as a factor rather than an exclusion. Until then, the official account remains a precaution without a stated cause.