Suspected Router Failure Behind Nationwide US Flight Grounding

A suspected failure involving network routers used by the US Federal Aviation Administration (FAA) has been blamed for a major disruption to air travel across the United States on Friday, 13 November 2026, forcing authorities to temporarily ground departing flights nationwide.

The incident, which lasted approximately five hours, affected thousands of flights and left passengers stranded at airports across the country. It has also raised serious questions about the reliability of America’s ageing air traffic control infrastructure.

The problem is believed to have started during routine maintenance work involving the replacement of older telecommunications equipment. Investigators are now examining whether a newly installed router was responsible for overwhelming parts of the FAA’s communications network.

According to US Transportation Secretary Sean Duffy, the new equipment generated an unusually high volume of network connection requests, reportedly exceeding 1,000 attempts every four to five seconds. This placed considerable pressure on older network equipment, resulting in communications instability and inconsistent data being received by air traffic control facilities.

The disruption affected 17 of the FAA’s 22 regional en-route air traffic control centres, which are responsible for managing aircraft travelling between airports.

L3Harris equipment under investigation

Attention has turned to US defence and technology contractor L3Harris, which was carrying out work to replace ageing copper telecommunications connections with modern fibre-optic infrastructure.

Officials are investigating whether the company installed a faulty router or whether the equipment was incorrectly configured during the upgrade.

Duffy said investigators were examining several possibilities, including user error, installation mistakes or defective hardware. No definitive cause has yet been established.

L3Harris has confirmed that it is supporting the FAA’s investigation into the incident.

The company says it has already completed more than 70% of the planned conversion from legacy copper connections to fibre-optic communications.

Why were all flights grounded?

The FAA took the unprecedented precaution of issuing a nationwide ground stop after communications problems affected air traffic control operations.

It is important to clarify that this did not mean aircraft already flying were ordered to immediately land. Planes already airborne were allowed to continue towards their destinations, while departing flights were temporarily prevented from taking off.

Officials considered the situation serious enough to suspend departures rather than risk aircraft operating with unreliable communications and data.

The nationwide restrictions were eventually lifted at approximately 8:15pm Eastern Time on Friday after engineers had stabilised the affected systems and carried out checks.

However, the disruption continued after the restrictions were removed, with airlines facing thousands of delayed and cancelled services as aircraft and flight crews were left out of position.

Reuters reported on Saturday that the disruption had affected more than 20,000 flights.

No evidence of a cyberattack

US officials have stressed that there is currently no indication that the incident was caused by a cyberattack or deliberate malicious activity.

Homeland Security Secretary Markwayne Mullin said the available evidence pointed towards a telecommunications failure rather than a hostile attack against US infrastructure.

Investigators are continuing to examine the equipment and network activity to establish exactly what happened.

Ageing infrastructure raises further concerns

The incident has once again highlighted concerns about the age of America’s air traffic control infrastructure.

Some of the equipment involved in the communications network is reportedly around 25 years old, with the US government already undertaking a major programme to modernise the country’s air traffic control systems.

Congress has previously approved $12.5 billion towards upgrades, while the Department of Transportation is seeking further funding to accelerate the modernisation programme.

The latest incident demonstrates how introducing modern technology into older infrastructure can create unexpected problems if the systems are not fully compatible.

With millions of passengers relying on the US aviation network every day, the FAA will now face pressure to establish exactly how a routine equipment upgrade could trigger a nationwide disruption.