Most flights in the United States were barred from taking off for about five hours Friday after new technology added to the nation's air traffic control system overloaded older parts of it, Trump administration officials said.
The overload caused "intermittent" communications and radar gaps, officials said. The ground stop was the longest nationwide in 25 years.
Thousands of flights were affected. The stop was lifted Friday evening, and a limited number of domestic flights began departing late that night.
Homeland Security Secretary Markwayne Mullin told reporters at the White House that no one was in danger and that more than 3,000 flights landed safely.
Mullin said the Federal Aviation Administration was installing "new equipment, new technology" and "it was overwhelming the older system." He said there appeared to be no indication of a cyberattack.
Transportation Secretary Sean Duffy said he could not guarantee it would not happen again.
Airlines face a slower recovery. With so many planes and crews out of position, a full return to normal will likely take days. Officials said they expect the system to be back to normal in time for the Thanksgiving travel rush.
