(Nov 14): US authorities halted flights nationwide for the longest stretch since the September 2001 terrorist attacks, in a major disruption that lays bare the frailty of America’s air traffic control infrastructure.

A handful of international flights were allowed to depart a few hours into the grounding, but crowds of passengers were left stranded at airports across the US nearly two weeks before the Thanksgiving holiday, with little indication of when travel would resume. 

The Federal Aviation Administration announced the ground stop for all airports in an advisory on its website Friday afternoon, saying that all departing traffic should remain halted until further notice. The agency later said a temporary telecommunications outage was to blame.

“Every flight has been accounted for and international flights will be handled on a case-by-case basis,” the FAA said.

This marks the third nationwide ground stop in US history, following a 2023 issue with the FAA’s safety notification system for pilots and dispatchers, and the Sept 11 terrorist attacks in 2001.

Department of Homeland Security Secretary Markwayne Mullin told reporters there was no indication the ground stop was due to a threat, and cautioned that it would take “some time” for the issue to be resolved.

Transportation Secretary Sean Duffy said a communication issue was affecting all air route traffic control centres, which manage aircraft en route at high altitudes.

“FAA technicians are investigating the issue,” Duffy said in a social media post. “We will provide immediate updates as we have them.

Shares of major US airlines, including JetBlue Airways Corp, Delta Air Lines Inc and American Airlines Group Inc, fell after the close of regular trading, while rental-car firms like Hertz gained.

The FAA has been dealing with outages across its air traffic facilities in recent years due to outdated equipment. The agency embarked on a massive overhaul effort last year to address the problems after obtaining US$12.5 billion from Congress.

Duffy has been seeking an additional US$30 billion for the effort. His department wrote a letter, co-signed by the Office of Management and Budget, to re-up the request this week.

Mullin told reporters that his department can’t rule anything out, including a potential link to artificial intelligence.

After his comments, Air Space Intelligence Inc, the Boston-based startup that the FAA recently tapped for its Strategic Management of Airspace, Routes and Trajectories system, said in a social media post that it’s not to blame.

“The current ground stop is not based on or a result of the SMART system, any product of ASI or our integration with FAA and ATC,” the company said.

ASI’s artificial intelligence tool debuted in a limited capacity around Washington in September. This month, the FAA announced a nationwide rollout across all 22 air route traffic control centres to help manage holiday travel and reduce delays.

The US Federal Bureau of Investigation doesn’t believe the stoppage is due to a cyber-attack or criminality, a person familiar with the matter said. One area of inquiry is whether the outage was caused by a software update, the person said.

US airlines had diverted over 800 flights as of 7.50pm New York time Friday, according to Cirium. About 670 of those 827 flights returned to their origin airport, while the remaining were diverted to a different one. 

As of late afternoon New York time, some 11,000 flights and over 1.5 million passengers were scheduled to fly.  

United and JetBlue said in separate statements that flights already airborne would continue, and domestic flights wouldn’t depart while the ground stop remains in place. United cancelled a significant number of Friday evening flights, while JetBlue cancelled nearly all remaining flights, the carriers said later.

The widespread disruption on Friday evokes recent memories of chaos in September when a fibre optic cable was cut by construction crews at Amtrak, triggering a cascading havoc that hit airports across the Northeast.

Airlines for America, the trade group that represents the largest US carriers, said in a statement that it’s in close communication with the FAA and the Transportation Department about the issue. 

Canada’s air navigation service provider Nav Canada confirmed in a post on X that “systems are operating normally” in the country. “There is currently no impact to our operations,” it said. “We continue to support the safe movement of air traffic in our airspace, including any aircraft that may be diverted.”

Air Canada said in an emailed statement that “ground stop is impacting flights to and from the United States”, and that “flights to and from the Caribbean and South America may also be impacted”.

The Vancouver International Airport said that it is “seeing delays for US-bound departures as well as some international flights that would fly over the US”.

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