SJ Airport Recovers From Nationwide Ground Stop as Officials Trace Outage to Router Fault During FAA Contractor Upgrade

Operations at Luis Muñoz Marín International Airport (SJU) were back to operating without restrictions Saturday, a day after a nationwide ground stop halted flights to and from the island. Aerostar Puerto Rico expects the airport to return to its usual pace starting Sunday.

The Federal Aviation Administration (FAA) lifted the order at about 8:15 p.m. Eastern Friday (9:15 p.m. in Puerto Rico) after more than four hours, according to Transportation Secretary Sean Duffy.

It was the first nationwide halt of departures since January 2023 and the longest since the Sept. 11 attacks.

In its notice Friday night, Aerostar said service was resuming gradually and that a return to normal could take time because of the accumulated effect on airline schedules, aircraft and crews.

U.S. officials now trace the failure to work on the FAA’s telecommunications network at a remote site, where a router began flooding other routers with data. The FAA has not said whether the cause was a defective router or an installation error, and said it has found no sign of a cyberattack.

Gradual recovery at SJU

Nelman Nevárez, Aerostar’s operations director, told the press Saturday that passenger movement at the airport was “quasi-normal” and that “after today, we will gradually recover normality.”

He advised passengers to turn on notifications in their airlines’ apps for first-hand updates on delays, cancellations and rebooking options.

The airport estimated that about 5,900 arriving and 5,100 departing passengers were affected by cancellations and prolonged delays, about 11,000 in total, according to published reports. Between eight and 10 flights were canceled during the stoppage.

Some flights left late Friday night, while others were canceled mainly because crews reached their maximum duty time.

The more lasting problem was aircraft out of place. Between 28 and 30 planes were sitting at SJU on Saturday morning when they were scheduled to be elsewhere, which complicated the day’s first departures, per the airport’s estimates.

What officials say went wrong

Duffy said the outage began during work at a remote FAA site, where the agency’s contractor, L3Harris, was replacing an old copper line with fiber. A router involved in the work began flooding other routers in the system with more than 1,000 connection attempts every four to five seconds, he said, disrupting communications with aircraft and some radar feeds.

Preliminary findings, according to unnamed government sources cited in published reports, point to Cisco 600 series routers made between 2001 and 2006, though other officials described conflicting information.

“We haven’t determined what the fault was,” Duffy said, adding that officials are checking whether there was “incompetence” or a faulty router. FAA Administrator Bryan Bedford said a review will determine whether the router was installed or configured incorrectly or was defective.

Bedford also acknowledged a structural weakness: the FAA has backup communications channels, but they all run on the same system.

“We have one federal telephony infrastructure,” he said. Officials had earlier described the cause more broadly as an “incredibly old” air traffic control system whose aging components were overwhelmed by newer technology. Homeland Security Secretary Markwayne Mullin said there were no indications of a cyberattack and that “there was never any lives at risk.”

The national toll and what comes next

U.S.-wide, FlightAware counted more than 9,100 flight cancellations and about 7,200 delays Friday, with American, Southwest, Delta and United each canceling more than 1,100 flights.

Airspace was operating normally by 7:30 a.m. Eastern Saturday and Duffy said the system was “back at full operations,” but more than 4,000 flights had been canceled by late morning as airlines repositioned aircraft and crews. Bedford had expected 4,000 to 5,000 cancellations among about 41,000 scheduled Saturday flights.

“I do think the worst is behind us,” Bedford said, adding that the FAA expects schedules to normalize by the close of business Sunday.

Duffy said he expects the system to operate normally for Thanksgiving travel, which begins in less than two weeks.

Delta, United, Southwest and American have waived change fees and fare differences for affected travelers, and the FAA says travelers can be rebooked or refunded.

The outage has sharpened a funding debate. Congress previously approved $12.5 billion toward modernizing air traffic control, which Duffy described as a down payment, and the administration raised its request late Friday to $50 billion.

New York Gov. Kathy Hochul called for Duffy’s resignation, and Sen. Tammy Duckworth called for an investigation.