Copper wire replacement cause of US' nationwide ground stop

Secretary of Transportation Sean Duffy said Saturday a contractor replacing a section of the system's old and discontinued copper wire with new fiber wire in a remote location Friday afternoon triggered the nationwide ground stop in the US.

That kind of work has been happening across the country and across industries for decades, according to Duffy.

Officials also assured passengers the US airspace was safe and operational after a nationwide ground stop that was initiated out of caution caused massive travel disruptions.

The longest flight stoppage in 25 years lasted more than four hours and ended around 8:15pm ET Friday, allowing some domestic flights to take off from US airports.

Of the 41,000 flights schedulled Saturday, more than 6,400 had been cancelled by Saturday night, according to FlightAware. More than 800 flights schedulled for Sunday were canceled, it said.

But officials said the air traffic control system was operational and expected airline schedules to fully recover by the end of Sunday, smoothing out ahead of the Thanksgiving travel rush.

Secretary of Homeland Security Markwayne Mullin said there was no indication the failure was related to a cyberattack and no lives were at risk.