The Federal Aviation Administration (FAA) has issued a nationwide ground stop for all US airports because of a communication issue affecting all air route traffic control centres, US Transportation Secretary Sean Duffy said.

FAA technicians are investigating the issue, Duffy added on Friday.

"Traffic should remain ground stopped until further notice," the FAA said in an advisory. "International flights will be managed on a case by case basis."

The last nationwide ground stop occurred in January 2023 due to a pilot alert system outage. Before that, the measure had not been implemented since the September 11, 2001 attacks.

Nearly 7,000 US flights have been delayed or cancelled due to nationwide groundstop, tracker FlightAware said.

The US government has been working to overhaul the outdated technology that air traffic controllers rely on since Congress approved $12.5 billion for the project last year.

Miles of old copper wires have been replaced with fiber optic lines and old radio systems are gradually being replaced at airports across the country.

But much work remains.

Duffy has said that another $30 billion will be needed to complete the work, and the White House has begun lobbying Congress to approve it.

This is a developing story and will be updated as details emerge.