Transport Secretary Sean Duffy attributes nationwide flight ground stop to infrastructure upgrade failure

WASHINGTON — A nationwide ground stop that grounded flights across the continental United States for more than four hours stemmed from an issue during a routine copper wire infrastructure upgrade, Transport Secretary Sean Duffy said.

No flights were permitted to take off from the continental US beginning at 15:54 EST on Friday. The stoppage marked the longest such grounding since the September 11, 2001, terrorist attacks, leaving persistent travel delays in its wake.

Speaking at a news conference, Duffy explained that a router undergoing maintenance as part of a transition from copper wire to fibre optics began flooding air traffic control systems with data. The technical malfunction triggered severe communication issues with aircraft, prompting federal authorities to shut down airspace as a safety precaution.

Duffy stated that investigators are examining whether the failure stemmed from faulty equipment or contractor incompetence. Contractor L3Harris was carrying out the communications modernisation work. Duffy noted that the United States relies on an antiquated telecommunications network, adding that the wire being replaced was so old it was being discontinued.

Federal Aviation Administration head Bryan Bedford told reporters that authorities found “zero evidence of anything nefarious, and zero evidence of anything AI related.” Duffy added that the government has found no indication of a cyber-attack, though formal investigations by the FAA remain active.

L3Harris acknowledged the incident in a statement on Saturday, reporting that it had completed over 70% of the infrastructure modernisation work prior to the shutdown. The company stated it is fully cooperating with the FAA’s ongoing inquiry.

The disruption triggered severe knock-on effects nationwide. According to tracking data from Flight Aware, more than 3,500 flights were cancelled and over 2,000 delayed on Saturday. Some passengers remained stranded on aircraft tarmacs for hours, while select international flights were permitted to depart to ease airport congestion.

Duffy warned that similar technical failures could recur without broader federal intervention, pointing to US President Donald Trump’s request for $30.1bn to fund comprehensive air traffic control upgrades. Both chambers of the US Congress are currently controlled by the Republican Party.

Former Transportation Security Administration administrator John Pistole noted that restoring operations within four and a half hours demonstrated systemic resilience, while questioning whether similar vulnerabilities remain unaddressed.