Departing flights across the United States have resumed after the Federal Aviation Administration (FAA) lifted a nationwide ground stop imposed over a telecommunications failure that disrupted air traffic control and caused widespread travel chaos.
The ground stop, imposed at 3:54pm Eastern Time, remained in effect for more than four hours. Airlines cancelled more than 4,700 flights and delayed 10,000 others on Friday, while another 700 cancellations had already been recorded for Saturday, according to flight-tracking service FlightRadar24. Aviation analysts warned that it could take days for airlines to restore their schedules.
The disruption also spread beyond the United States, forcing cancellations of flights from Canada and Europe.
The Department of Homeland Security said there were no signs that the outage had been caused by a cyberattack, although authorities were examining possible causes.
"There is no indication as of yet that this was a nefarious attack against us. It's just a telecommunications outage as of right now," Homeland Security Secretary Markwayne Mullin told reporters outside the White House.
"There's no reason for the public to be afraid or scared for your loved ones. This isn't another 9/11," he added.
Mullin said the department was examining all possible causes, including a new AI-powered air traffic control system.
The Homeland Security chief said there was no immediate evidence of a deliberate attack behind the disruption, which affected air traffic control communications across the country.
The FAA said the nationwide ground stop followed a communications failure affecting air traffic control centres. Technicians were investigating the problem.
The agency described the measure as a precaution taken for safety reasons, saying a temporary telecommunications outage had affected its operations.
Departures were suspended across US airports, while incoming international flights were to be managed individually. Aircraft already in the air were allowed to continue to their destinations and land safely.
The outage also affected aircraft arriving at US airports, with some left waiting on taxiways as airport gates filled up.
The incident came amid heightened concern over the reliability of the country's air traffic control infrastructure, which has faced repeated equipment failures, communications problems and shortages of controllers.
The disruption left passengers stranded at airports and caused widespread delays and cancellations.
More than 4,700 flights were cancelled and 10,000 delayed on Friday, according to FlightRadar24. Another 700 flights had already been cancelled for Saturday, as airlines struggled to manage the disruption caused by the nationwide grounding.
Major airlines, including United and American, warned passengers of widespread disruption. Some travellers were left waiting aboard aircraft or returned to departure gates as airport operations were affected.
The shutdown also left arriving aircraft stranded on taxiways as airport gates filled up, while passengers crowded departure halls and airline counters from Boston to Seattle and New York to Los Angeles.
The disruption affected aircraft already in the air, although those flights were allowed to land. The FAA said every flight had been accounted for.
The incident marked only the second nationwide ground stop since the September 11, 2001 attacks. The previous one came in January 2023, when the FAA suspended domestic departures following a computer failure affecting its Notice to Air Missions (NOTAM) system.
That disruption lasted around 90 minutes.
Friday's communications failure renewed scrutiny of the ageing US air traffic control infrastructure, which has faced repeated calls for modernisation.
The incident came as the White House and Transportation Department urged Congress to approve an additional $30.1 billion to upgrade the country's airports and air traffic control system.
In a letter to lawmakers, Transportation Secretary Sean Duffy and Office of Management and Budget Director Russell Vought said the investment was critical to modernising the national airspace.
"This investment is critical to complete the modernisation of our national airspace - delivering a resilient telecommunications backbone for air traffic controllers, modern hardware and software, state-of-the-art control towers, and world-class airport infrastructure," they wrote.
Congress had already approved $12.5 billion over five years in July 2025 to upgrade air traffic control infrastructure and increase the recruitment of controllers. The latest funding request seeks additional resources for a broader overhaul of the system.
Much of the FAA's air traffic control technology is decades old. The agency also announced on November 5 that it would replace outdated floppy-disk-based systems used for weather and other critical information at more than 400 air traffic control facilities by the end of 2028.
The upgrade will replace four systems dating back to the 1980s with a consolidated digital platform.
The FAA has experienced similar communications-related outages in recent years, although these have generally affected individual airports or regions rather than the entire national aviation network.
In September, thousands of flights across the northeastern United States were delayed or cancelled after a circuit failure at a Philadelphia air traffic facility and the accidental severing of a fibre-optic cable in New Jersey disrupted FAA operations.
The precise cause of Friday's nationwide disruption remained unclear, with authorities continuing to investigate the communications failure.
