US President Donald Trump said on Friday that the nationwide flight disruption was unlikely to have been caused by a cyberattack or artificial intelligence, as authorities continued to investigate the telecommunications outage that prompted the Federal Aviation Administration (FAA) to impose a ground stop across the country.US Homeland Security Secretary Markwayne Mullin also said there was no indication that a national security threat was behind the disruption, seeking to distinguish the incident from the September 11, 2001, attacks.“This isn’t the same comparison to 9/11,” Mullin told reporters outside the White House, assuring them that all flights had been accounted for and passengers were safe.Mullin said authorities had no reason to believe the communications failure was linked to a threat against the United States, although he did not rule out any possible cause, including a cyberattack.“There is no indication that we’ve had, no reason to believe, that as of right now this was a threat to the United States,” he said, adding that there was “no indication as of yet that this was a nefarious attack against us.”“This was a telecommunication outage,” Mullin said.The Homeland Security Secretary confirmed that Trump had been briefed on the FAA’s nationwide ground stop and had spoken with Transportation Secretary Sean Duffy. He said the President had taken an active role in coordinating the response and ensuring that officials had the necessary resources.“He was on the phone earlier with the president and several of us. And they’re doing a phenomenal job in a crisis mode,” Mullin said, referring to the coordination among officials.He added that Trump “took a lead in this immediately” to ensure the situation was managed.Mullin also dismissed any connection between the FAA telecommunications outage and a major Microsoft outage reported a day earlier.“I don’t see any reason to connect those two at all,” he said, adding, “Those are separate issues.”The FAA had earlier ordered a nationwide ground stop after a temporary telecommunications outage affected all 22 Air Route Traffic Control Centers, disrupting flight operations across the country.Duffy announced the disruption in a post on X, saying FAA technicians were investigating the communications failure.“The @FAAnews issued a nationwide ground stop for all U.S. airports following a communication issue impacting all Air Route Traffic Control Centers. FAA technicians are investigating the issue. We will provide immediate updates as we have them,” Duffy said.The FAA said the suspension was a precautionary measure and that international arrivals would be handled on a case-by-case basis.“There has been a temporary telecommunications outage – out of an abundance of caution all flights have been halted. Every flight has been accounted for and international flights will be handled on a case by case basis,” the agency said in a post on X.According to flight-tracking platform FlightAware, around 7,000 flights were delayed or cancelled following the ground stop. The disruption affected all 22 regional air traffic control centres, which are responsible for guiding aircraft within their respective regions.Data from Flightradar24 showed that around 4,042 flights were airborne and heading towards US airports when the ground stop was issued.The precise cause of the telecommunications outage remained unclear. An airline source told CNN that the FAA was still investigating the disruption and had yet to establish what had happened.“The FAA doesn’t know yet what is going on; it is affecting different facilities in different ways,” the source told CNN, adding that a crisis call had been held without a clear explanation for the outage.Mullin said authorities were continuing to assess the situation, reiterating that all flights had been accounted for and passengers were safe.