Transportation Secretary Sean Duffy said a nationwide FAA ground stop on November 13 followed work to replace an aging copper communications line with fiber optic infrastructure at a remote agency facility. Speaking at a press conference, Duffy described the replacement as routine maintenance rather than a broader major modernization project.
According to Duffy, the existing copper line was being discontinued, making its replacement necessary. He said a newly installed router subsequently flooded other routers in the air traffic control system with more than 1,000 connection attempts every four to five seconds, disrupting radar feeds and communications between controllers and aircraft.
The underlying cause remained undetermined. Duffy identified several possibilities, including faulty hardware, an incorrectly configured router, or errors by contractor L3Harris. His comments outlined potential explanations rather than a confirmed finding. L3Harris said it was supporting the FAA investigation into the conditions that led to the nationwide air travel disruption.
Duffy also called on Congress to provide additional funding for air traffic control modernization. He said lawmakers had provided only part of the money needed to complete the work. While describing the incident as maintenance related, he said the FAA was pursuing its broader modernization program quickly while prioritizing safety.
In its statement, L3Harris said it was upgrading communications infrastructure supporting the National Airspace System in coordination with the FAA. The company said that, together with telecommunications partners and the agency, it had completed more than 70 percent of the planned conversion from legacy copper wiring to fiber optic systems.
L3Harris said safety and reliability were its highest priorities and acknowledged the impact on travelers, airlines and air traffic operations. Its statement did not identify a specific cause or address each possibility Duffy raised. The account, updated November 14, left the underlying technical explanation unresolved while the FAA investigation continued.