The root cause of the longest halt in flight departures to U.S. airports since 9/11 remains unclear, U.S. transportation officials said at a Saturday press conference. Routers and networking equipment appeared to be involved in the technological disruption that grounded flights across the country, but a definitive cause had not been established as of Saturday afternoon.

Bryan Bedford, administrator of the Federal Aviation Administration, told reporters that the agency could not pinpoint the reason for the infrastructure malfunctions and therefore took actions that led to the grounding order. "Because of our lack of identifying the root cause, we were unwilling to take any risk that this propagation could actually result in a sensor losing connectivity with aircraft," he said. "What we saw was instability. We couldn't explain the instability."S1S2

Officials reported issues with routers and networking equipment on Saturday, citing products and services from Cisco and L3Harris Technologies. Transportation Secretary Sean Duffy said, "Until I can build [the new architecture], I'm stuck with L3Harris, who owns this network." In a statement on X, L3Harris said that it, in partnership with other tech companies, has completed more than 70% of the planned airspace communications conversion from legacy copper wires to a fiber-optic system, and that it is supporting the FAA's investigation into the conditions that led to the Nov. 13 ground stop.S1S2

On Friday, Duffy and Department of Homeland Security Secretary Markwayne Mullin called for an overhaul of air travel, with Duffy requesting $50 billion from Congress. Bedford, however, said that router updates were a matter of ordinary business for the agency and were distinct from the $12.5 billion FAA modernization effort. "We are constantly replacing 2,000, you know, Cisco 600 routers with Juniper routers, right? So this is ordinary course of business stuff," he said. "So let's not conflate those two things."S1S2