FAA Ground Stop Is Over: What Caused the Nationwide Outage and What It Means for Your Flight

The Federal Aviation Administration lifted its nationwide ground stop at 8:15 p.m. ET on Friday, Nov. 13, after a communications failure in the air traffic control system halted departures at every U.S. airport for 4 hours and 21 minutes. Flights are moving again, but the shutdown stranded passengers across the country overnight, and some airlines warned that delays and cancellations would spill into Saturday.

Officials say there is no sign so far of a cyberattack. The exact cause has not been determined.

What happened

Radar and communications problems began shortly after 3:30 p.m. ET, ABC News reported. At 3:54 p.m. ET the FAA ordered a ground stop for all U.S. airports, citing extraordinary circumstances and safety. Planes already in the air were allowed to continue to their destinations, and flights within Alaska and Hawaii were still allowed to depart.

Transportation Secretary Sean Duffy said about 3,500 planes were in the air when the order was issued. Flight-tracking site Flightradar24 counted 4,042 flights heading to U.S. airports at that moment, according to Al Jazeera.

By 7:30 p.m. ET, FlightAware data showed more than 10,000 U.S.-related delays and more than 4,200 cancellations, NBC News reported. The Associated Press estimated that about 1.5 million passengers were affected.

The disruption reached beyond U.S. borders. Departures from Europe to the U.S. were suspended at the FAA's request, and Mexico asked U.S.-bound aircraft to stay on the ground. Canada's air navigation provider, Nav Canada, said its own systems were not affected.

What caused it

Duffy blamed aging equipment. He said switches and routers in the air traffic control network became overloaded with data, which made radar and communications unstable. He described the network as an old system that still runs on analog telecommunications. According to Al Jazeera, radar and communications were never lost completely.

Homeland Security Secretary Markwayne Mullin said there was no indication of a malicious cause and that the outage did not appear to be a cyberattack, but he said investigators were not ruling anything out. Bloomberg reported, citing an official, that the FBI does not believe a cyberattack or other crime was involved and is examining whether a software update played a role.

Attention has also turned to SMART, an AI-based traffic management tool that the FAA expanded to all 22 of its regional en route control centers on Nov. 10. Its developer, Air Space Intelligence, said the ground stop was not caused by the system, and Duffy said there was no way it could have triggered the outage. Mullin said officials are still looking at it.

What it means for your flight

• Check before you go. Confirm your flight status in your airline's app before leaving for the airport. JetBlue canceled the rest of its Friday flights and said it expected disruption to continue on Saturday.
• Refunds. Under U.S. Department of Transportation rules, if your flight is canceled and you choose not to travel or turn down the rebooking you are offered, the airline must refund your ticket, whatever caused the cancellation.
• Rebooking. American Airlines issued a travel alert that includes the option of a refund. Southwest said customers whose flights were canceled can rebook to another date without a penalty.
• Hotels and meals. Airlines usually cover these only when a delay is within their control. An FAA outage generally is not, so ask your airline what it is offering before you book a hotel yourself.

Why it matters

This was only the third nationwide ground stop in U.S. history, after the Sept. 11 attacks in 2001 and the January 2023 failure of the NOTAM system, which sends safety notices to pilots. It came less than two weeks before Thanksgiving, the busiest travel period of the year.

Duffy said he expects the system to be fully running for the holiday, but he warned that more outages like this one are likely until the old equipment is replaced. The administration has asked Congress for about $30 billion to modernize air traffic control, on top of $12.5 billion approved last year. Duffy has said a full overhaul would take $50 billion.

Lawmakers want answers. Sen. Tammy Duckworth called for a thorough investigation, and Sen. Maria Cantwell said the Senate Commerce Committee will review what went wrong.

What we don't know yet

The FAA has not said what exactly failed first or why the problem spread to every regional control center at once. Officials have not given a timeline for the investigation, and estimates of how many flights were canceled vary between data sources and keep changing as airlines update their schedules.

Around Prague, based on reporting by ABC News, NBC News, Al Jazeera, FAA

Cover photo: Noah Wulf / Wikimedia Commons, CC BY-SA 4.0, cropped