The nationwide shutdown of US air travel on Friday may have been caused by a single faulty router installed by government contractor L3Harris, US officials said on Saturday, as the aviation system struggled to recover and more than 5,000 further flights were cancelled.
The Federal Aviation Administration grounded all departures across the country for nearly five hours on Friday, the biggest disruption to American air travel since the September 11 attacks, after communications faltered at 17 of its 22 en route control centres. More than 20,000 flights have been disrupted since Friday, according to Reuters.
Transportation Secretary Sean Duffy told a news conference on Saturday that L3Harris had been carrying out routine maintenance to switch telecommunications lines from old copper wire to fibre at at least one remote location when the trouble began. Officials told Reuters there may have been problems with routers installed in Arkansas and Texas.
According to Duffy, the new routers began flooding other routers with more than 1,000 connection attempts every four to five seconds, overloading the system. FAA chief Bryan Bedford said controllers reported radio frequencies “going in and out” and having to switch between primary and backup systems. Because the agency could not immediately explain why so many facilities were affected at once, it ordered the nationwide ground stop. None of the centres actually went dark, Bedford said.
Whether the fault lay with the installation or the equipment itself has not yet been determined. “We’re working to determine whether we had incompetence, meaning was it user error or installer error from L3Harris, or did they install a faulty router? We haven’t determined what the fault was,” Duffy said. “This was an FAA system that didn’t meet the moment,” he added, promising to hold people accountable. The cause remains unconfirmed and the FAA is still investigating.
The routers at the centre of the incident are about 25 years old and were supposed to have been replaced in 2006, Duffy said. The FAA spends $1 billion a year maintaining its ageing copper-wire network, and about 30 per cent of the lines have yet to be converted to fibre. L3Harris said it had completed more than 70 per cent of the planned conversion and was supporting the FAA’s investigation.
Officials were emphatic that the outage was not an attack. “We see zero evidence of anything nefarious, and zero evidence of anything AI-related,” Bedford said.
Bedford said the worst was behind the system and full recovery could be expected on Sunday, ahead of a busy week of travel before Thanksgiving. As of 1pm Eastern time on Saturday, more than 5,000 flights had been cancelled and over 4,400 delayed, according to tracking service FlightAware. Duffy asked Congress for further investment in the Department of Transportation, and outgoing House Speaker Mike Johnson said Republicans would use the remaining 50 days of their majority to authorise more spending on the FAA.
Sources: Reuters, “US aviation shutdown blamed on L3 Harris installed router”, https://www.reuters.com/business/aerospace-defense/us-aviation-shutdown-blamed-l3-harris-installed-router-2026-11-14/ ; CNN, “What we know about the cause of the nationwide FAA ground stop”, https://www.cnn.com/2026/11/14/politics/faa-ground-stop-what-we-know
