US flights resume after nationwide ground stop of nearly four hours is lifted

Flights have resumed across the United States after a ground stop of nearly four hours at the nation's airports. US Transportation Secretary Sean Duffy announced at a White House press briefing on Friday local time that aircraft were moving again at all airports in the country.

Earlier, flight operations were temporarily halted at airports across the United States because of a communications problem. The hours-long shutdown led to large numbers of cancelled and delayed flights nationwide and left countless passengers stranded at airports.

Duffy told reporters that after about four hours, aircraft were flying again in US airspace. Explaining the cause of the disruption, he said it had happened ‘because of old hardware’.

US Homeland Security Secretary Markwayne Mullin had earlier rejected suggestions that the disruption was caused by a cyberattack or a glitch involving artificial intelligence (AI). He said there had been no cyberattack and that the incident had nothing to do with Microsoft.

Duffy said the same: flights had not been halted because of a cyberattack or the Microsoft outage, he said.

President Donald Trump has been briefed on the incident. Officials have said there is no immediate threat to the United States.