US Transportation Secretary Sean Duffy and Federal Aviation Administration (FAA) Administrator Bryan Bedford said on Saturday that Friday’s four-hour nationwide flight ground stop began when government contractor L3Harris installed a router during a telecom upgrade that flooded the air traffic control network with connection requests. Speaking at a Transportation Department briefing in Washington, the officials said FAA staff needed 45 minutes to locate the fault because maintenance work is still logged manually on paper.
The stoppage on Friday, Nov. 13 was the longest nationwide grounding of US flights since the Sept. 11, 2001 attacks. L3Harris, which owns and operates the FAA’s legacy telecommunications network, was swapping discontinued copper wiring for fiber-optic lines when a newly installed router began bombarding other routers on the network. Duffy said at the Saturday briefing, “Specifically, we had over 1,000 connection attempts every four to five seconds. And what that did was give us issues with our communication with airplanes and it also caused some disruption with our radar feeds.”
The flood caused voice, ground communication, and radar instability across 17 of the FAA’s 22 en route air route traffic control centers, though Bedford said at Saturday’s press conference, “No facilities went dark. Nothing was fully lost.” In a statement on Saturday afternoon, the contractor confirmed it was assisting the federal inquiry and said, “L3Harris takes the nationwide ground stop and its impact on travelers, airlines and air traffic operations seriously.”
Paper maintenance logs delayed the FAA response
When communications became unstable on Friday afternoon, aviation officials could not immediately see where the upgrade work was happening. Bedford told reporters that because maintenance is recorded manually on paper, personnel had to pore through physical documents for 45 minutes to figure out who was working on what part of the network. With more than 3,500 airplanes in the sky, Bedford ordered a precautionary halt to all domestic departures while technicians tracked down the source of the outage. According to the BBC, the FAA announced the ground stop at 15:54 EST (20:54 GMT) and reopened the skies at 20:15 EST, while CBS News reported the initial order went out at 15:36 EST and was lifted around 20:20 EST.
Federal investigators are now examining why the hardware failed during a routine copper-to-fiber transition. Duffy said on Saturday, “So what we’re working to determine was whether we had incompetence, meaning was it user error or install error from L3Harris or did they install a faulty router? We haven’t determined what the fault was.” Duffy also said the agency would re-evaluate whether to allow contractors to perform network upgrades during daytime travel hours. Unnamed senior government sources told CBS News the fault was isolated to Cisco 600 series routers manufactured between 2001 and 2006. Officials have not publicly named the exact facility where the work took place; unnamed officials told Reuters there may have been issues with routers installed in Arkansas and Texas, while AvBrief reported the installation centered on a router in Chicago.
The timing of the maintenance drew criticism from former federal security officials. Juliette Kayyem, who served as US assistant secretary of Homeland Security under President Barack Obama, questioned why the upgrade was carried out on a busy Friday travel day rather than staged in smaller steps with backup systems ready to step in if the network came under threat. The Professional Aviation Safety Specialists (PASS) union stated that its FAA technicians were not involved in the upgrades. Homeland Security Secretary Markwayne Mullin and President Donald Trump both said there was no indication of a cyberattack, national security threat, or link to an earlier Microsoft outage.
Thousands of weekend flight cancellations across the US and Europe
Even after the FAA lifted the order on Friday night and Duffy said on Saturday that the airspace system had returned to full operations, airlines spent the weekend untangling displaced aircraft and crews. According to FlightAware figures cited by the BBC, airlines recorded nearly 8,000 cancelled flights and more than 8,500 delays in the US on Friday, followed by more than 5,900 cancellations and over 7,000 delays on Saturday. CBS News, citing FlightAware at a different cutoff, reported 9,159 cancellations and 7,190 delays on Friday and more than 5,000 cancellations and roughly 5,300 delays on Saturday, while aviation analytics firm Cirium estimated that 1.5 million passengers were stranded on Friday.
According to a Dawn report, Bedford offered a “sincere apology to the American travelling public” on Saturday as major carriers trimmed their weekend schedules. The BBC reported that Delta Air Lines and United Airlines each cancelled 20% of their Saturday flights, American Airlines cut 520 journeys, and JetBlue cancelled 40% of its schedule, whereas Dawn reported Saturday cancellation rates of about 25% for Delta, United, and American and nearly 45% for JetBlue. Internationally, Eurocontrol suspended US-bound departures across its 42 member states between 22:00 UTC on Friday and 05:00 UTC on Saturday, Sydney Airport temporarily grounded US-bound flights, Air Canada cancelled cross-border services, and London Heathrow reported delays and cancellations on US routes. Because air traffic control outages fall outside airline control, carriers are not liable for extra cash compensation under US, UK, or European Union rules, though the US FAA Reauthorization Act of 2024 entitles passengers on cancelled or significantly delayed flights to refunds or fee-free rebooking.
Aging infrastructure and the push for a $50 billion overhaul
L3Harris, formed in the 2019 merger of Harris Corporation and L3 Technologies, has held FAA telecommunications contracts since 2002. Both Bedford and L3Harris said roughly 70% of the agency’s copper lines have now been converted to fiber after 25 years of work, a transition Canada completed in 18 months. Congress approved $12.5 billion in 2025 to modernize the air traffic system, though Congressional critics noted in a joint statement that the administration has spent only $1 billion of that allocation so far. Calling the US network “a house that’s about to be condemned,” aviation analyst Miles O’Brien told the BBC, “I think most of us could look at this and go ‘this is a system in the United States that we have allowed to decay’. It is worse than a fixer-upper.” Duffy estimated on Saturday that a complete overhaul of the air traffic control system will cost $50 billion, up $20 billion from his earlier request to Congress. Bedford projected that US flight schedules would return to normal by the close of business on Sunday, Nov. 15, while the FAA and L3Harris conduct further testing on the network.