United States (US) authorities have said concerns over a possible cyber-attack prompted the involvement of the FBI and intelligence officials after a communications malfunction grounded flights across the country for several hours.

The nationwide disruption, which halted flight departures for about four hours, was linked to maintenance work on the country’s ageing air traffic control system, according to US Transportation Secretary Sean Duffy.

Duffy said work was being carried out to replace old copper wiring with fibre technology by contractor L3Harris when the system began experiencing intermittent communications and radar gaps, making it unsafe for flights to continue.

L3Harris had yet to comment on the incident.

Department of Homeland Security Secretary Markwayne Mullin said the new equipment appeared to have overwhelmed the existing system, although authorities were still investigating the possibility of a cybercrime.

“That new equipment, new technology, just wasn’t – it was overwhelming the older system,” Mullin said.

Duffy said FBI Director Kash Patel and Director of National Intelligence Jay Clayton were briefed on Friday after officials became concerned that the disruption could have resulted from a cyber-attack.

The comments came as airlines across the United States worked to recover from the disruption, which left hundreds of thousands of passengers stranded and forced some travellers to spend the night at airports.

About 15,000 flights were delayed or cancelled during the shutdown, with more than five per cent of scheduled flights across the country affected.

Passengers travelling from the United Kingdom to the United States also experienced delays, although most services were gradually returning to normal.

Duffy apologised to travellers affected by the disruption but maintained that safety remained the priority.

“Is it disruptive? Of course… People may not get to a wedding, people may not get to a birthday party, they may not get home from a work trip. I want them to get home safely,” he said.

The Transportation Secretary also renewed his call for Congress to provide additional funding to modernise the country’s air traffic control infrastructure.

According to Duffy, a new state-of-the-art air traffic control system would cost about $50 billion.

“I hope that they meet this moment,” he said.

Authorities, meanwhile, expressed optimism that the worst of the disruption had passed as airlines continued efforts to restore normal flight schedules. (Sunday Tribune)