Washington DC [US], November 14 : US Homeland Security Secretary Markwayne Mullin on Friday (local time) said authorities had found no evidence so far that a telecommunications outage which triggered a nationwide Federal Aviation Administration (FAA) ground stop was caused by a cyberattack or rogue artificial intelligence, but stressed that investigators were not ruling out any possibility. 
Responding to whether he could say with 100 per cent certainty that the disruption was not caused by a cyberattack or rogue AI, Mullin said the available evidence pointed towards a mechanical failure, although investigations were continuing.
“There's nothing completely certain right now. It doesn't appear that way. We've activated our teams...This is a national emergency. We have all of our assets...There is nothing that indicates it yet," Mullin said.
Explaining why authorities had not detected signs of a cyberattack, the Homeland Security Secretary said there had been no suspicious online activity, claims of responsibility or identifiable traces of an intrusion into the affected systems.
"Now when we start looking at cyber threats, cyber attacks, typically some people are going to raise their hand up and say we did that, there's no chatter, we haven't seen any footprints, as you would say, or identifications of people that got into the system. It appears that this was mechanically driven. However, we're still looking, so we're not going to rule that out," he added.
Mullin also described the disruption as a national security concern, backing Transportation Secretary Sean Duffy's demand for congressional funding to replace the country's ageing air traffic control infrastructure.
"I want to hit back on to what Secretary Duffy said with the funding. This is a national security risk. We just saw what took place when we have vulnerabilities and we have old systems," he said.
"The President has declared this a national emergency, and now we have to have Congress act and fund it. This is vitally important that we get this system built," Mullin added.
The Homeland Security Secretary further criticised the lack of priority given to modernising the country's air traffic control infrastructure, arguing that the latest disruption demonstrated the risks associated with prolonged delays in upgrading critical systems.
"The President has said this, Secretary Duffy has said this multiple times, our Air Traffic Control system is outdated and it hasn't been a priority from Congress. And so this is what happens when Congress kicks the can down the road," he said.
The remarks came after the FAA lifted the nationwide ground stop imposed across US airports following a telecommunications outage that disrupted air traffic control operations, triggering thousands of flight delays and cancellations.
Duffy had earlier attributed the technical failure to ageing telecommunications infrastructure, explaining that radar and communication systems at air traffic control centres and Terminal Radar Approach Control (TRACON) facilities experienced instability at approximately 3:36 pm local time.
He said air traffic controllers began receiving inconsistent radar data and communication signals from aircraft, prompting authorities to activate established safety procedures and halt flights as a precaution.
Duffy said more than 3,500 aircraft were airborne when the ground stop was issued, adding that authorities coordinated their safe landing. He also clarified that critical operations, including medical evacuation flights, cargo movements carrying essential medicines and law enforcement activities, were allowed to continue.
According to Duffy, the country's legacy telecommunications equipment, which operates on an analogue system, became overloaded with data, resulting in inconsistencies in information transmitted through its switches and routers. Newer Internet Protocol (IP) switches installed under the Trump administration continued functioning during the disruption, he said.
The Transportation Secretary renewed the administration's appeal to Congress for bipartisan funding to build an entirely new air traffic control system rather than relying on incremental repairs.
Meanwhile, the FAA confirmed that all flights had been accounted for, while international arrivals were handled on a case-by-case basis.
According to flight-tracking platform FlightAware, approximately 7,000 flights were delayed or cancelled following the disruption.
The outage also prompted airlines to issue travel advisories. Air India warned of possible consequential disruptions to its flights to and from the United States, advising passengers to check their flight status before travelling to airports.