The FAA’s November 13, 2026 nationwide ground stop stemmed from a telecommunications outage in its aging air traffic control network during routine contractor maintenance. Transportation Secretary Sean Duffy stated that L3Harris was switching copper lines to fiber at a remote site when a router began flooding the system with over 1,000 connection attempts every few seconds, overloading switches and producing inconsistent radar and voice data. Officials have ruled out cyberattacks and AI involvement but remain uncertain whether the root cause was faulty equipment (Cisco 600-series routers from the early 2000s), configuration errors, or installation mistakes by the contractor. A full root-cause analysis is pending, while the incident has intensified calls for billions in modernization funding to replace legacy TDM infrastructure.