Duffy Says Router Overload Triggered Nationwide U.S. Flight Ground Stop

Transportation Secretary Sean Duffy said a router overloaded after a fiber-optic upgrade at a remote location, prompting Friday’s nationwide flight halt and an investigation into the equipment failure.

Duffy said L3Harris was replacing copper wire with fiber-optic cable during routine maintenance. He said officials were trying to determine whether the problem stemmed from user error, an installation error by L3Harris or a faulty router.

Two locations were pinging the network at a rate of 1,000 connections every four to five seconds, FAA acting Chief Technology Officer Rebecca Guy said. She said the FAA disabled both locations, stabilizing the network, and began a root-cause analysis.

More than 8,200 flights were canceled Friday evening, and at least 3,000 more were canceled Saturday as disruptions continued. The new details add to earlier coverage of the L3Harris system update and ground stop.

The ground stop came a day after the FAA announced an artificial intelligence tool for air traffic controllers. FAA Administrator Bryan Bedford said the agency had seen no evidence of a malicious or AI-related cause.

Duffy said officials would reevaluate when the work is scheduled. Switchovers at larger airports are scheduled late at night, while remote-site switchovers take place during the day, he said.