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Problems arose while upgrading the United States' decades-old communications network, causing the longest nationwide flight disruption since the September 11, 2001, attacks.
U.S. Secretary of Transportation Sean Duffy said on the 14th that this incident occurred during the process of replacing part of the core system that enables communication between air traffic controllers and pilots from copper wire to optical fiber. The existing copper wire was so old that production had already been discontinued.
On the 13th, flights in the United States were halted for more than four hours, affecting thousands of flights and passengers.
Earlier, U.S. Secretary of Homeland Security Markwayne Mullen said there were no signs of a cyberattack and everyone was safe.
We have summarized what has been confirmed so far.
What caused the suspension of flight operations?
On the afternoon of the 13th, L3 Harris, a U.S. government contractor, was working to improve aviation communications networks.
L3 Harris installed a 'router' in a remote area in the United States, replacing copper wires with optical fiber. A router is a device that specifies the path for data to travel in a communication network.
According to Minister Duffy, the router overloaded the network by sending 1,000 connection attempts every four to five seconds to other routers in the air traffic control system.
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Federal Aviation Administration (FAA) Administrator Brian Bedford said this caused voice and ground communications to become "unstable" in 17 of the country's 22 air traffic control centers.
It took aviation authorities 45 minutes to determine where the problem occurred. This is because maintenance work details were recorded manually on paper documents.
Administrator Bedford acknowledged that because of this, the FAA had to "comb through" paper documents "to figure out who was doing what."
He explained that the decision was made to ground all flights as a precaution while the cause of the problem was traced.
Aviation expert Miles O'Brien compared the U.S. air traffic control system to "a house about to be demolished."
He told the BBC, "Most people will look at this situation and think, 'The United States has allowed the system to become old and broken,'" and added, "It has gone beyond the point where it can be simply repaired."
Minister Duffy said the system would need to be completely overhauled and estimated it would cost about $50 billion.
He said he would first investigate whether the failure was due to "incompetence" or faulty equipment.
He said he would also "reexamine" the issue of allowing system improvement work during daylight hours.
L3 Harris said in a statement on the afternoon of the 14th that it is working with the FAA to modernize aviation communications infrastructure and is cooperating with the FAA's investigation.
“L3 Harris takes seriously the nationwide flight disruption and its impact on travelers, airlines, and air traffic operations,” the company said.
Juliette Kayem, who served as the U.S. Assistant Secretary of Homeland Security during former President Barack Obama's term, questioned why the system improvement work was carried out on Friday, one of the busiest days of the week for airline users.
“We don’t do that on Fridays when a lot of our air traffic controllers are working,” he said.
“We need to find ways to minimize the impact of system improvement work, for example by not working on the entire system at once,” Kaim added. “At the same time, we need to have a fallback system in place that can be deployed immediately if the improvement work starts to pose a threat to the system in any way.”
“We are cooperating with the FAA’s investigation to determine the circumstances that led to the suspension of flights across the United States on November 13,” a L3 Harris spokesperson said.
“L3 Harris takes seriously the nationwide flight disruption and its impact on travelers, airlines and air traffic operations,” he added.
How many flights were affected?
According to flight tracking site FlightAware, more than 8,500 flights were delayed and about 8,000 were canceled due to the suspension of aircraft operations on the 13th.
In its first announcement at 3:54 PM ET (8:54 PM GMT), the FAA announced that all flights departing within the United States will be prohibited from taking off until further notice.
At the time, over 3,500 aircraft were operating in the sky. Some aircraft were diverted to other airports, while others continued their flights to their scheduled destinations.
A few hours later, some flights were allowed to take off at San Francisco International Airport.
The FAA allowed aircraft operations again at 8:15 PM Eastern Time.
What happened to the international flights?
All flights from Eurocontrol (European Air Navigation Safety Organization) member countries to the United States have been suspended.
Eurocontrol has 42 countries, including dozens of European Union (EU) member states, the United Kingdom, Turkmenistan, Israel, and Morocco, members.
Passengers departing from the UK were warned that flight operations may be disrupted on the morning of the 14th.
Several flights from Heathrow Airport to the United States were canceled or delayed. However, Manchester Airport said no major disruptions were expected, and flights at Gatwick Airport continued to operate normally.
Sydney Airport, Australia's largest international airport, has also suspended all flights to the United States, but scheduled flights are currently expected to depart as planned.
Air Canada also canceled flights between the U.S. and Canada.
When will flight operations return to normal?
Minister Duffy announced on the 14th, “All operations have returned to normal.”
However, as he predicted the day before, it is taking time to resolve the aftermath of this incident.
According to FlightAware, more than 5,900 flights were canceled and more than 7,000 were delayed in the United States on the 14th.
Delta Air Lines and United Airlines said they were resuming operations, but both airlines canceled 20% of their scheduled flights on the 14th. American Airlines canceled flight 520.
Meanwhile, JetBlue canceled 40% of its scheduled flights.
What rights do passengers have?
In the United States, the United Kingdom, and the European Union, if a flight is determined to be delayed due to reasons beyond the airline's control, such as an aircraft defect or a pilot's illness, the airline may be liable for compensation.
Therefore, airlines are not obligated to pay compensation to passengers for delays caused by air traffic control problems.
However, passengers still receive a certain level of protection under U.S. federal law and the laws of each country.
According to the US Federal Aviation Administration Reauthorization Act of 2024, if a flight is canceled or 'substantially delayed,' airlines must provide alternative transportation or provide a full refund of the ticket price if the passenger abandons boarding.
Here, ‘significant delay’ means a delay of more than 3 hours for domestic flights and 6 hours for international flights.
Additionally, this law stipulates that all airlines provide refunds within 7 business days of requesting a refund for tickets purchased with a credit card, and within 20 days for tickets purchased using other payment methods. Passengers who accept alternative flights will not be eligible for a refund.
In the United States, airlines are not required to provide meals or lodging to passengers, but some airlines may offer free assistance to customers.
However, passengers traveling from the UK to the US or using UK airlines may have additional rights.
Under UK law, airlines have a duty of care to passengers if their flight is delayed or canceled for any reason.
This includes support for:
If the airline fails to provide such assistance, passengers have the right to use the necessary services themselves and then be billed later.
The UK's Civil Aviation Authority (CAA) advises passengers to keep their receipts and not spend more than necessary.
When was the last time flights were grounded across the United States?
This is the second time that such a flight suspension has occurred across the United States since the September 11, 2001, hijacking of an airplane by al-Qaeda.
Dr Guy Gratton, associate professor of aeronautics at Cranfield University in the UK, told the BBC: "This appears to be the worst since 9/11, but it is certainly not on the same scale."
Dr. Gratton mentioned a case in the United States in 2023 where aircraft operations were halted due to a failure in the ‘Air Mission Notification’ (Notam) system.
He explained, “At that time, the suspension of operations lasted for 1 hour and 52 minutes, and about 9,500 flights were delayed and about 1,300 flights were canceled.”
At the time of the system failure that occurred in 2023, aviation safety-related notices could no longer be issued, and aircraft operations were suspended until the system was restored.
