One Single Router Blamed for US Ground Stop, Duffy Says

He said the system saw "over 1,000 connection attempts every four to five seconds." That caused communication problems with planes and disrupted radar feeds, so the ground stop was ordered.

Investigators have not settled the cause. Duffy said they are still working to determine whether "contractor error or a faulty piece of equipment" was to blame.

Scale of the disruption

FlightAware, a website that tracks flights, said more than 4,100 flights had been canceled. The effects spread around the world and forced professional and college sports teams to find alternate transportation.

Aviation consultant Andrew Charlton said the stoppage hit about a quarter of the 45,000 flights in the US each day. Charlton, managing director of Aviation Advocacy, said aircraft keep moving from city to city, so one grounding ripples outward.

"The knock-on effect of that is incredible," he said. Long-haul and international flights across the Atlantic or Pacific make it worse, he added.

The nationwide stop was the first since January 2023, when another key FAA computer system that sends notices to pilots malfunctioned. It was the second since the September 11, 2001, attacks.

Funding dispute

Duffy blamed Congress for failing to approve more money for new technology. He played down the fact that implementing fixes had overtaxed the system, and he suggested more disruptions might occur.

Charlton said the work is hard because the system can never shut down. "What you're watching here is trying to change the tires of your car when the car's going at 80 miles an hour down the expressway," he said.

The FAA has already replaced thousands of old copper wires with fiber optic lines and upgraded hundreds of radio systems. The overhaul began last year after Congress approved $12.5 billion in funding.

Duffy and the White House are pushing for $30 billion more to finish the work. Officials say the system will likely return to normal in time for the Thanksgiving travel rush.