Miami International Airport
Aircraft sit at Miami International Airport on Friday, after the FAA ordered a nationwide ground stop. The shutdown was lifted later that evening, but airlines warned of continued delays and cancellations. Getty Images

The Federal Aviation Administration lifted its nationwide ground stop Friday evening after a telecommunications failure brought departing flights across the United States to a halt for more than four hours, leaving thousands of travelers stranded and airlines facing disruptions that could last for days.

Transportation Secretary Sean Duffy said U.S. airspace reopened at 8:15 p.m. ET, but warned that flights would not immediately return to normal schedules.

"At 8:15 tonight, Eastern time, we've opened up the airspace," Duffy said during a White House briefing, according to CBS News.

He urged passengers to check directly with their airlines, warning that getting aircraft back into position and clearing the backlog would take time.

More than 4,700 flights were canceled and 10,000 delayed Friday, with another 700 flights already canceled for Saturday, according to Flightradar24 data cited by Reuters.

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Duffy attributed the communications failure to aging technology, saying routers handling air traffic control data had become overloaded and started producing inconsistent information.

"What we have is an incredibly old air traffic control system," Duffy said.

He explained that the routers were overwhelmed by data, prompting authorities to shut down operations as a precaution.

Multiple sources told CBS News that an update to a private communications network connecting the nation's air traffic control system triggered a reboot, followed by a system crash. The network is operated by L3Harris, which had not immediately responded to the broadcaster's request for comment.

Homeland Security Secretary Markwayne Mullin said the introduction of newer technology into the older system had overwhelmed it, describing the incident as a major engineering problem.

Mullin said there was no indication of a cyberattack or deliberate interference.

The shutdown began shortly before 4 p.m. ET after communications problems affected the 22 regional air traffic control centers responsible for directing aircraft between airports.

The FAA initially ordered departing aircraft to remain grounded, citing extraordinary circumstances and safety concerns. Flights already airborne continued to be managed by controllers.

According to Associated Press live updates, the restrictions also disrupted international travel, with European authorities suspending U.S.-bound departures and Mexico temporarily grounding flights heading to American airports.

JetBlue canceled its remaining domestic flights Friday evening, while other airlines diverted aircraft or adjusted schedules.

The disruption also affected cargo operations and left several college sports teams struggling to reach their destinations for weekend games.

Duffy said approximately 3,500 aircraft were in U.S. airspace when the shutdown began. By the time officials briefed reporters Friday evening, that number had fallen to fewer than 400.

Friday's shutdown was the longest nationwide grounding since the Sept.11, 2001, terrorist attacks, Reuters reported. The FAA previously imposed a nationwide ground stop in January 2023 following a malfunction in its aviation safety notification system.

Congress approved $12.5 billion for air traffic control modernization in 2025, but federal officials have said substantially more funding is needed to replace outdated equipment.

Mullin estimated that a complete overhaul could cost approximately $50 billion.

Although the nationwide restrictions have been lifted, passengers were advised to expect further cancellations and delays as airlines worked to restore operations.