The Federal Aviation Administration ordered a nationwide ground stop Friday afternoon, freezing departures at airports across the United States for roughly four to five hours in only the third such emergency order in the agency's history — following the September 11, 2001 attacks and a 2023 system-wide outage.

The stop took effect at 3:54 p.m. ET and grounded flights nationwide before being lifted around 8:15 p.m., according to CBS News. Thousands of flights were canceled or delayed, and travelers at major hubs described hours stuck on tarmacs and in terminals as departure boards filled with red.

Transportation Secretary Sean Duffy said the shutdown traced back to aging air traffic control technology and data-overloaded routers, not a cyberattack. Homeland Security Secretary Markwayne Mullin said the FAA had layered new technology onto an old system, "causing the massive breakdown," and both officials said the incident was unrelated to a separate, days-long global Microsoft Outlook and Teams outage that had been disrupting businesses the same week, according to NBC News.

Not everyone is buying the explanation

CNN reported that some air traffic controllers privately said they "don't buy" Duffy's account of what went wrong, even as the White House insisted there was no evidence of a "nefarious act." The FAA has faced years of warnings about outdated equipment and chronic understaffing in its control towers, long before Friday's shutdown became the clearest public demonstration of the system's fragility.

"I BELIEVE THAT IT'S GOING TO TAKE US SOME TIME TO GET BACK TO CAPACITY."

That was Duffy's blunt assessment of the days ahead, delivered as airlines scrambled to rebook stranded passengers. He also used the moment to press Congress for new funding to modernize the system, warning bluntly: "You will have more of these" without an infrastructure overhaul, according to Al Jazeera.

Airlines including Delta, United and Southwest issued system-wide travel waivers as cancellations rippled into the weekend. Flights have resumed, but officials cautioned that full capacity could take days to restore — a reminder, aviation officials say, that Friday's scare is unlikely to be the last.