The DHS secretary said there were no indications of a cyberattack.
The Federal Aviation Administration ordered a rare nationwide ground stop for all airports Friday -- a more than four-hour disruption that snarled travel from coast to coast with canceled flights and stranded passengers.
At a White House news conference Friday night, Transportation Secretary Sean Duffy blamed old technology that became overloaded and called on Congress to provide billions more in funding to modernize critical equipment, calling the situation an "emergency."
Department of Homeland Security Secretary Markwayne Mullin told reporters there was no indication the incident stemmed from a cyberattack, but that officials were still investigating.
Thousands of flights were canceled amid the ground stop.
"I believe that it's going to take us some time to get back to capacity," Duffy said when asked how long air travelers should expect delays and cancellations to continue.
The Federal Aviation Administration ordered a nationwide ground stop Friday for all airports due to a communication issue affecting air traffic control.
The agency's alert said the stop was "due to extraordinary circumstances and for reasons of safety."
