US flights were grounded after a telecommunications outage prompted a nationwide ground stop, Homeland Security Secretary Markwayne Mullin said at the White House.
Mr Mullin said there was no indication at present that the disruption had been caused by a cyberattack, although officials were not ruling out any possibility.
“There is no indication, and we had no reason to believe as of right now, that this was a threat to the United States,” he told reporters. “[But] we’re not ruling out anything at this point.”
He also said there was no reason to link the telecommunications problem with the outage that affected Microsoft systems around the world the previous day.
Mr Mullin sought to reassure families that people already in the air were safe and would be brought back to the ground. “There’s no reason for the public to be afraid or scared for their loved ones. This isn’t another 9/11,” he said.
