Routine work replacing copper telecommunications lines with fibre-optic equipment has been linked to the nationwide US flight grounding on Friday 13 November, according to Transportation Secretary Sean Duffy. The contractor involved was L3Harris Technologies, but officials have yet to determine whether faulty equipment or installation error caused the failure.
Speaking at a briefing on Saturday 14 November, Duffy said a router involved in the changeover flooded other parts of the Federal Aviation Administration (FAA) network with connection attempts, destabilising information used by air traffic controllers. The ground stop has been lifted, but disruption to airline schedules continued into Saturday.
This is a new development in the nationwide shutdown first reported by Fish 4 News. It identifies the maintenance operation under investigation, although it does not establish the final technical cause or legal responsibility.
What did Sean Duffy say caused the FAA shutdown?
The US Department of Transportation’s official briefing states that L3Harris was conducting routine maintenance at one or more remote FAA locations, replacing ageing copper telecommunications lines with fibre and converting connections from older analogue technology to internet protocol systems.
Duffy said a router associated with that work started sending excessive connection attempts through the network. The FAA recorded more than 1,000 connection attempts every four to five seconds, according to his account. That interfered with communications and radar information being supplied to air traffic control facilities.
The secretary said investigators were examining whether the problem came from an installation mistake or a defective router. No final root-cause finding has been announced. His criticism of L3Harris should therefore be understood as an allegation and preliminary government assessment, not proof that the contractor was negligent.
How did one upgrade affect flights across America?
On Friday, the FAA said communications issues were affecting multiple air route traffic control centres. Duffy subsequently placed the start of network instability at about 3.36pm Eastern Time on 13 November, after which the agency stopped departures nationwide as a safety precaution. The ground stop was lifted at 8.15pm Eastern Time (1.15am GMT on Saturday).
Reuters reported that instability affected 17 of the FAA’s 22 en-route control centres. Officials stressed that the affected centres had not all gone dark, but some data and communication links had become unreliable. That distinction matters: a network can continue functioning while its inconsistent information makes routine flight operations unsafe.
Duffy said more than 3,500 aircraft were airborne during the incident and praised controllers and pilots for managing the situation. The Department of Transportation said more than 8,000 flight operations resumed on Friday evening after restrictions were lifted.
What has L3Harris said?
L3Harris told Reuters that it took the incident seriously and was helping the FAA investigate the conditions leading to the 13 November ground stop. The contractor said it had completed more than 70% of the planned conversion from legacy copper connections to fibre optics.
Reuters also reported that officials were examining possible router problems in Arkansas and Texas. The precise site or sites involved, the sequence of faults and any responsibility for the malfunction have not been established in a published technical report.
Were the ageing FAA systems or modernisation programme to blame?
FAA Administrator Bryan Bedford drew a distinction between the routine maintenance involved in this incident and the separate $12.5 billion national air traffic control modernisation programme. He said the FAA routinely maintains the older telecommunications network and replaces its ageing routers. It would be misleading to describe Friday’s work as a failed installation under the newer programme without evidence.
There is, however, a broader oversight issue. A September 2026 Government Accountability Office audit found that the separate modernisation programme lacked a reliable lifecycle cost estimate and an integrated schedule across 11,389 individual projects. That report is relevant context for the challenge of renewing US aviation infrastructure, not a finding about the cause of Friday’s router incident.
Duffy said the FAA would reassess the timing of some maintenance work. He explained that smaller remote sites had traditionally been upgraded during daytime hours because the work was not expected to cause widespread disruption.
Was the nationwide ground stop caused by a cyberattack?
Officials said they had found no evidence pointing to a cyberattack. Duffy said the network stabilised after technicians isolated the work being carried out at the remote location. Bedford also said officials had not seen evidence linking the incident to the FAA’s newer AI-supported systems. These are the authorities’ current findings, not a completed independent technical investigation.
How many flights were disrupted, and when will schedules recover?
Reuters said more than 20,000 flights had been disrupted since Friday, including cancellations and delays. That figure describes the wider effects on airline operations and should not be read as the number of flights grounded simultaneously. It will also change as airlines recover and flight-tracking services update their totals.
The FAA said the airspace was operating again on Saturday, although cancellations and delays were continuing as airlines tried to reposition aircraft and crews. Bedford said airlines expected to restore normal schedules by the end of Sunday 15 November. That was an expectation, not a confirmed recovery.
Passengers travelling between Britain and the United States should check flight status directly with their airline, including connecting flights, before setting off for an airport. The lifting of the FAA restriction does not guarantee that any individual flight will depart on schedule.
What happens next?
The FAA is carrying out a root-cause analysis. Among the key questions are whether the router was defective or wrongly configured, why network instability spread so widely, whether redundant paths worked as intended and whether maintenance procedures need to change. The agency has not yet published a final investigation assigning fault.
For related reporting, read our examination of FAA backup safeguards and the earlier update confirming the ground stop had been lifted.
Sources
- US Department of Transportation, 14 November: Sean Duffy and Bryan Bedford briefing
- US Department of Transportation, 13 November: Ground stop lifted
- Federal Aviation Administration, 13 November: Nationwide ground stop statement
- Reuters, 14 November: L3Harris response and network effects
- Government Accountability Office, September 2026: Air traffic control modernisation planning audit
Follow the story
Fish 4 News will track the FAA’s root-cause findings, any confirmed accountability measures and changes to maintenance or network safeguards. See our developing FAA ground stop coverage.
