Luc Rongier -
3 hours ago In summary
• FAA ground stop ended, but 15,000+ flights were canceled• A router issue during FAA upgrades caused nationwide disruption
• Aging air traffic tech is under scrutiny; delays may continue
The nationwide FAA shutdown that brought U.S. air travel to a near standstill Friday is over, but the damage is still spreading through airports across the country.
More than 15,000 flights were canceled across Friday and Saturday as airlines struggled to recover from the extraordinary nationwide ground stop, with thousands more delayed and additional cancellations already appearing for Sunday.
Now federal officials say they have identified what appears to have triggered the crisis.
The disruption began while government contractor L3Harris was performing routine work to replace an aging copper telecommunications connection with fiber at a remote FAA facility. During that work, a router began flooding other parts of the air traffic control network with connection attempts, destabilizing communications and some radar data across much of the country.
Transportation Secretary Sean Duffy said investigators are now trying to determine whether the failure resulted from a faulty router, an installation mistake or contractor error.
For travelers, the immediate shutdown may be over. But the cascading effects are expected to continue as airlines reposition aircraft, crews and passengers after one of the most disruptive days in modern U.S. aviation.
More Than 15,000 Flights Were Canceled in Two Days
Friday’s nationwide ground stop lasted more than four hours and prevented roughly 12,000 flights from operating as scheduled.
Commercial airlines canceled approximately 9,000 to 10,000 flights Friday alone, depending on the reporting cutoff. The problems continued into Saturday.
By Saturday afternoon, more than 5,300 U.S. flights had been canceled and roughly 6,300 delayed, according to FlightAware figures reported by Reuters. By Saturday night, the Associated Press put the cancellation total above 6,400 for the day.
That pushes the combined Friday-Saturday cancellation count beyond 15,000 flights.
And the disruption was not finished.
More than 800 Sunday flights had already been canceled by Saturday night as airlines continued trying to rebuild their schedules.
The FAA said the airspace itself was open and its systems were stable, but passengers were warned that delays and cancellations could persist while airlines worked through the backlog.
Officials Now Say a Router Problem Triggered the Nationwide Crisis
The technical explanation emerging from federal officials is striking because of how ordinary the work initially appeared.
L3Harris, a longtime FAA telecommunications contractor, was replacing an aging copper connection with fiber at a remote facility.
The FAA is gradually moving parts of its communications infrastructure from older analog technology to newer digital systems, and officials described the work as routine.
But something went badly wrong.
According to Duffy, a router involved in the transition began sending more than 1,000 connection attempts to other routers every four to five seconds.
That flood of data began overwhelming parts of the network.
The resulting instability affected 17 of the FAA’s 22 en-route air traffic control centers, creating problems with communications used to coordinate aircraft and disruptions involving some radar feeds.
Controllers did not completely lose communications or radar nationwide, but federal officials said the inconsistent data was serious enough that allowing thousands of additional aircraft to take off would have created an unacceptable safety risk.
The FAA responded by stopping departures across the country.
Investigators Are Looking at L3Harris, but the Exact Failure Has Not Been Determined
Federal officials are now examining whether the router itself was defective or whether something went wrong during its installation.
« We’re working to determine whether we had incompetence, meaning was it user error or install error from L3Harris, or did they install a faulty router? » Duffy said Saturday.
L3Harris has not been formally blamed for the outage.
The company said it was supporting the FAA’s investigation to determine exactly what conditions produced the November 13 ground stop.
L3Harris has worked with the agency for more than two decades and owns the legacy telecommunications network currently used by the FAA.
The company says more than 70% of the planned conversion from older copper connections to fiber has already been completed.
The incident therefore raises an uncomfortable question for federal officials: how could what was supposed to be a relatively routine infrastructure upgrade create a failure severe enough to disrupt air traffic across the entire country?
The FAA Says This Was Not a Cyberattack
The scale of the shutdown immediately generated speculation about whether U.S. aviation infrastructure had been hit by a cyberattack.
Federal officials say they have found no evidence of one.
Duffy said systems returned after the FAA isolated the work being performed at the remote facility, leading authorities to believe the outage was technical rather than malicious.
FAA Administrator Bryan Bedford also said there was no evidence connecting the incident to artificial intelligence.
A separate Microsoft service outage was not responsible for the FAA disruption either.
The investigation is instead focused on the telecommunications network and the router activity that destabilized it.
America’s Aging Air Traffic Control Technology Is Now Under Intense Scrutiny
The outage has also exposed a much larger problem.
Some of the technology supporting the U.S. air traffic control system is decades old.
The FAA spends about $1 billion every year simply maintaining its legacy telecommunications network, according to federal officials.
Some routers being replaced are around 25 years old. Duffy said equipment involved in the broader network should have been replaced years ago.
The agency is still working to eliminate copper communications lines, decades-old computer systems and other technology that has remained in service far beyond the lifespan travelers might expect from infrastructure controlling one of the busiest airspaces in the world.
Congress has already provided $12.5 billion for air traffic control modernization.
Following Friday’s shutdown, Duffy said he would seek an additional $50 billion for upgrades to air traffic control and airport infrastructure.
« This was an FAA system that didn’t meet the moment, » Duffy said.
This Is Not the First Small Technical Failure to Cause Nationwide Travel Chaos
The incident has uncomfortable parallels with another major FAA failure.
In January 2023, the agency issued its first nationwide ground stop since September 11, 2001 after its NOTAM system, which distributes critical safety information to pilots, failed.
That disruption ultimately affected more than 11,000 flights.
Investigators later determined that contractors had unintentionally deleted computer files while working on the system.
Other recent FAA disruptions have been linked to severed fiber-optic cables, failed circuits and aging equipment.
Friday’s event may prove even more consequential because a problem associated with what officials described as routine network work was able to spread across 17 regional control centers before the FAA isolated it.
The Airspace Is Open Again, but Travelers Are Still Paying the Price
Officials say the national air traffic system is now stable. After the ground stop was lifted Friday night, more than 8,000 flight operations resumed, according to the Department of Transportation.
But reopening the airspace does not instantly repair an airline network.
Aircraft that should be in New York may be stranded in Chicago. Pilots and flight attendants may be out of position or may have reached federal duty-time limits. Passengers who missed connections need to be rebooked, while available seats on subsequent flights can disappear quickly.
FAA Administrator Bryan Bedford said operations were expected to be largely back to normal by Sunday, but individual airlines may recover at different speeds.
Passengers traveling this weekend should continue checking their flight status before leaving for the airport, even if their itinerary currently appears normal.
One Router May Have Exposed a Much Bigger Weakness
The extraordinary part of Friday’s crisis is not simply that a technical failure occurred.
It is how quickly that failure spread.
What began during routine work at a remote FAA location destabilized communications across most of the nation’s en-route control centers and ultimately forced authorities to halt departures across the United States. The ground stop is over.
The investigation into how one piece of network infrastructure could contribute to such an enormous failure is only beginning.
And after more than 15,000 cancellations in two days, millions of American travelers have already seen the consequences.
