Router under investigation after US aviation shutdown disrupts more than 20,000 flights

A single router installed by government contractor L3Harris may have triggered the nearly five-hour shutdown of the US aviation system on Friday, government officials said Saturday. More than 20,000 flights have been disrupted since the incident, which occurred as travelers began their weekend journeys.

Transportation Secretary Sean Duffy said L3Harris had been carrying out routine work to move telecommunications lines from copper wiring to fiber at at least one remote site. Officials told Reuters that routers installed in Arkansas and Texas may have experienced problems. Investigators have not established whether the disruption resulted from a faulty router, an installation mistake or user error.

The problem affected communications at 17 of the Federal Aviation Administration’s 22 en route centers. According to Duffy, new routers sent more than 1,000 connection requests to other routers every four to five seconds, creating difficulties involving aircraft communications and radar at FAA facilities. Unable to determine the underlying cause, the agency ordered a nationwide ground stop.

The FAA said communications remained operational, but data at the affected centers became unstable. The facilities did not go dark. Duffy said the routers being replaced were roughly 25 years old and had been scheduled for replacement in 2006. He also said officials would reconsider the timing of maintenance at smaller facilities to reduce the risk of further disruption.

L3Harris said it was treating the incident seriously and assisting the FAA’s investigation into the November 13 ground stop. The contractor said it had finished more than 70% of the planned conversion of airspace communications from copper lines to fiber optics. The FAA spends $1 billion a year maintaining the older copper network while pursuing its replacement.

The shutdown adds to a series of failures involving aging air traffic control infrastructure. In 2023, a contractor accidentally deleted files, prompting a 90-minute nationwide ground stop that disrupted 11,000 flights. That was the first nationwide halt since the September 11, 2001, hijacked aircraft attacks. Other failures in recent years have involved accidental fiber cuts and a melted component that produced a strong chemical smell.

In September, thousands of flights in the densely populated Northeast were delayed or canceled after two separate failures. A circuit failed at a Philadelphia air traffic facility, while a construction crew accidentally cut a fiber-optic cable in New Jersey. Officials said further failures would occur until the system receives adequate upgrades.

Congress has provided $12.5 billion to modernize the FAA’s air traffic control and telecommunications infrastructure. Duffy has requested another $50 billion for air traffic control and airports. The agency continues to use decades-old Compaq computers and replacement components purchased on eBay as it works to update its equipment.

Last week, the FAA said it would eliminate outdated floppy disks used for weather and other essential information at more than 400 air traffic control facilities by the end of 2028. Another modernization effort involves replacing paper flight strips used by controllers to track aircraft. That transition began in 2022, but implementation at 49 major airports is expected to take until at least 2028.