According to US Transportation Secretary Sean Duffy, unstable radar communications at air traffic control centres caused flight delays and temporary suspensions.

As reported by the Report news agency, citing The New York Times, the secretary disclosed this at a press conference held jointly with Homeland Security Secretary Markwayne Mullin.

Sean Duffy said that when the Federal Aviation Administration (FAA) issued an order to suspend flights, more than 3,500 aircraft were already in the air.

The transportation secretary attributed the disruption to the excessive ageing of the air traffic control system. Asked whether they could completely rule out the possibility that the incident had been caused by a cyberattack or uncontrolled artificial intelligence, Markwayne Mullin said that it was not possible to provide a 100 per cent guarantee at this stage. However, initial information indicated that neither had been the cause.

According to the publication, Sean Duffy has been seeking an additional $30 billion from Congress over the past several months to modernise the air traffic control system. Following the flight disruptions, the secretary announced that $50 billion would now be needed for this purpose.