A data-flooding problem destabilized the Federal Aviation Administration’s air-traffic communications network on Nov. 13, prompting a nationwide ground stop for departing flights. The FAA says instability reached 17 of 22 en-route centers. Investigators are examining work on a new router at one of two potential sites, but have not established the root cause, according to Reuters and NBC News.

The incident shows how a network problem at a remote facility can affect air-traffic operations across the country. It did not mean a total communications blackout: the FAA says some radio frequencies and radar feeds remained reliable, and aircraft already in the air landed safely.

What happened to the FAA network?

The FAA says the disruption began at about 3:30 p.m. Eastern on Nov. 13, when unusual data traffic made legacy equipment unstable. The agency reported about 1,000 connection attempts every four to five seconds on its FAA telecommunications network. The instability affected 17 of 22 air route traffic control centers and several terminal radar facilities.

As a safety precaution, the FAA stopped departures nationwide. It says the network was stable and air traffic resumed by 8:15 p.m. that day. The agency reports that approximately 3,500 aircraft landed safely during the incident and says it has no indication, based on available evidence, that the disruption was a cyberattack, according to its incident Q&A.

Did a new router cause the ground stop?

The cause is still under investigation. The FAA’s initial review identified two possible sources of the excess data: a radar site in Amarillo, Texas, and a radio communications site in El Dorado, Arkansas. L3Harris, the FAA’s network service provider, had been doing work at the Arkansas site, including deploying a new router. The FAA says L3Harris blocked both locations as the network stabilized.

That sequence does not establish that the router was defective or that the contractor caused the event. Transportation Secretary Sean Duffy told Reuters that officials had not yet determined whether the problem came from user error, installation work or faulty equipment. L3Harris says it is supporting the FAA’s investigation and has not announced a root-cause finding.

As a precaution, the FAA says it disabled the same functionality on about 60 similar routers while the investigation continues. L3Harris says it has completed more than 70% of its planned conversion of airspace communications from legacy copper wires to fiber-optic links. The company has not said that this modernization work caused the disruption.

How many flights were affected?

For Friday, Nov. 13, the FAA reported approximately 12,462 flight cancellations, including 9,082 by major airlines. The agency cautioned that not every cancellation was directly caused by the nationwide ground stop. The disruption followed a stop lasting nearly five hours, but the FAA says some communications and radar capability remained available throughout.

What the incident says about critical infrastructure

Air-traffic systems must keep operating while their communications infrastructure is upgraded. The FAA says its network was destabilized by excessive data traffic and that the ground stop was issued to protect safety. The event highlights the operational risk of dependencies that can spread instability across many control centers, even when the original problem is still being traced.

The FAA says operations are returning to normal and that it is continuing to investigate the system inconsistencies with L3Harris. Until that work is complete, the router should be treated as one element under examination—not as a confirmed cause.

Frequently asked questions

Was the FAA’s air-traffic system completely offline?

No. The FAA says some radio frequencies and radar feeds stayed reliable, allowing controllers to communicate with and track aircraft. The ground stop halted departures as a safety precaution.

Has the FAA confirmed that a faulty router caused the disruption?

No. The FAA and L3Harris are investigating. A new router had been deployed at one of two sites identified in the initial review, but the root cause has not been established.

Was the incident a cyberattack?

The FAA says it has no indication of a cyberattack or outside actor based on the evidence available to it.

How many flights were canceled?

The FAA reported approximately 12,462 cancellations on Nov. 13, while cautioning that not all were directly caused by the ground stop.

Sources:Federal Aviation Administration; Reuters; NBC News; L3Harris statement.