US Flight Ground Stop: What we know about disruption

The United States has lifted a nationwide flight ground stop that lasted more than four hours, marking the longest shutdown of departing flights since the September 11, 2001, terrorist attacks. The Federal Aviation Administration (FAA) attributed Friday’s disruption to what it described as “extraordinary circumstances” arising from a communications failure affecting air traffic control centres across the country.

Homeland Security Secretary Markwayne Mullin said there was no indication that the incident resulted from an attack, assuring that passengers and aviation personnel were safe throughout the disruption. Here are the major details of the incident. How many flights were affected? The ground stop resulted in more than 8,500 flight delays and nearly 8,000 cancellations on Friday, according to flight-tracking service FlightAware.

The FAA initially announced the restriction at 3:54 p.m. Eastern Standard Time (20:54 GMT), directing that all departing flights within the United States remain grounded until further notice. More than 3,500 aircraft were airborne when the order was issued. While some were diverted to alternative airports, others continued to their intended destinations.

Several hours later, the FAA began allowing limited departures, including flights from San Francisco International Airport. The agency officially reopened US airspace at 8:15 p.m. Eastern Time (01:15 GMT on Saturday). What happened to international flights? The disruption also affected international aviation, with flights bound for the United States from countries within the European Organisation for the Safety of Air Navigation, known as Eurocontrol, suspended at the FAA’s request.

Eurocontrol confirmed on its website that the suspension was due to technical problems affecting US aviation operations. The organisation has 42 member states, including European Union countries, the United Kingdom, Ukraine, Turkey, Israel and Morocco. Sydney Airport, Australia’s largest international airport, also grounded all US-bound flights pending further notice.

Air Canada equally cancelled flights between the United States and Canada. When will normal flight operations resume? Transportation Secretary Sean Duffy warned that the disruption would have consequences for airline operations over several days, even after the ground stop was lifted. “It’s going to take us some time to unwind what’s happened this afternoon,” he said at a news conference on Friday night.

Duffy disclosed that tens of thousands of passengers were stranded at airports across the country, with many uncertain about where they would spend the night. Major airlines announced different recovery plans following the reopening of US airspace. Delta Air Lines and United Airlines said they were resuming operations, while American Airlines said it was working to operate as many remaining flights as possible that evening.

JetBlue Airways announced that it would resume flights on Saturday morning. What caused the ground stop? Duffy attributed the disruption to an overloaded legacy telecommunications system used by the country’s air traffic control network. He explained that the system’s analogue switches and routers became overwhelmed by data, resulting in failures that affected communications and radar operations.

“So this is analogue telecom. Our switches, our routers actually got overloaded with data and they went down,” he said. The Transportation Secretary argued that the incident demonstrated the urgent need to overhaul the country’s ageing air traffic control infrastructure, estimating that the modernisation would cost about $50 billion. “It’s going to continue to fail,” he warned.

Meanwhile, Mullin said investigators had found “zero evidence” that the incident was caused by a cyberattack. He also ruled out any connection with the global Microsoft outage that began on Thursday, saying the introduction of some new technology into an ageing air traffic control system had overwhelmed the existing infrastructure. Both officials maintained that aviation safety was not compromised during the shutdown.

When was the last nationwide flight ground stop? Friday’s incident was only the second nationwide flight shutdown since the September 11, 2001, terrorist attacks, when authorities grounded aircraft across the country following the hijacking of commercial planes by al-Qaeda operatives. A previous nationwide grounding occurred in January 2023 after a technical failure affected the FAA’s Notice to Air Missions (NOTAM) system.

The system provides pilots with essential safety information, including potential hazards, airport facility changes and other operational notices. Dr Guy Gratton, an associate professor of aviation at Cranfield University, told BBC Verify that Friday’s disruption was the worst since September 11, although he noted that the scale was not comparable to the 2001 attacks.

He recalled that the 2023 shutdown lasted one hour and 52 minutes, delaying approximately 9,500 flight