A nationwide ground stop that halted flights for about four hours on Friday began when a contractor updated old Federal Aviation Administration telecommunication lines, Transportation Secretary Sean Duffy said Saturday.
Duffy said L3Harris, a longtime FAA contractor, was doing routine maintenance at a remote location and changing copper wire to fiber optics. The FAA is still investigating the exact error that began flooding other routers in the air traffic control system, and it has not determined whether L3Harris was responsible. FAA Administrator Bryan Bedford said there was no evidence of anything nefarious or any AI-related problem. L3Harris said it has completed more than 70% of its copper-to-fiber conversions and is supporting the investigation.
FlightAware counted nearly 25,000 delayed flights and more than 9,000 cancellations on Friday. Cirium reported more than 4,000 cancellations Saturday morning, or 18% of flights departing the U.S. Bedford said schedule problems should be resolved by Sunday evening. Passengers whose flights were canceled will be rebooked or receive a full refund, and they should contact their airlines directly.
The stop was the second nationwide ground stop since September 11, 2001. Duffy used the disruption to renew his call for more federal money for air traffic control upgrades. Congress approved $12.5 billion for modernization in July 2025.
At Tampa International Airport, travelers slept in chairs before security on Saturday morning. Fort Lauderdale-bound passengers stranded in Washington, D.C., spent hours waiting for rebooking help, and some switched to other airlines or drove.
