No commercial aircraft landed at Newark Liberty International Airport for nearly eight hours on Monday after both the primary and backup communications lines failed at the FAA's Philadelphia regional air traffic control facility.

The dual-line failure is the latest in a string of outages prompting Transportation Secretary Sean Duffy to ask Congress for an additional $20 billion. Flight tracking site Flightradar24 placed the Newark ground stop at approximately 9:40 a.m. to just after 5:20 p.m. local time. More than 200 flights into and out of Philadelphia International Airport were canceled. Disruptions rippled through LaGuardia and John F. Kennedy. By midday Tuesday, FlightAware.com showed nearly 100 flights still canceled because crews and aircraft were stranded out of position.

What triggered the dual-line failure?

A switch on the primary communications line at the Philadelphia TRACON failed Monday morning. When controllers transferred to the backup fiber optic line, they found it had been inadvertently severed by railroad construction workers. The facility lost both radar and radio contact for hours. The failed switch is among the equipment scheduled for replacement under the FAA's modernization plan.

The same Philadelphia facility experienced repeated radar outages in spring 2025 that led the FAA to restrict traffic at Newark, a key United Airlines hub. Communications failures have also hit regional centers serving Minneapolis last month and Dallas in September, disrupting American Airlines' primary hub and grounding flights across multiple states.

How much has been spent so far?

Congress appropriated $12.5 billion to the FAA last year for the air traffic control overhaul. The funding followed an American Airlines flight colliding with an Army Black Hawk helicopter over the Potomac River, killing 67 people in the deadliest U.S. aviation accident in more than two decades. The agency says it has since replaced 3,346 communications lines and 190 voice switches nationwide.

Duffy has called the existing appropriation a "down payment." He wants $20 billion more to redesign the underlying telecommunications architecture, move controller computing into the cloud, and deploy an AI-based system intended to predict equipment failures.

"I have money for some of the telecom replacing old copper wires," Duffy said on Fox News Tuesday. "Bringing in new fiber so it's faster. The problem is this is a 40-year-old architecture or design. I need new money to do a whole new design — a new architecture of telecom so it will never go down."

Could the dual failure have been prevented?

Sheldon Jacobson, a University of Illinois engineering professor whose research helped design TSA PreCheck, said the FAA should ensure backup systems operate independently of the primary feed and consider adding a third redundant connection.

"When any one of these systems goes down, it doesn't just affect that airport," Jacobson said. "Because these are major hubs, it affects literally dozens of other airports and literally thousands of passengers."

The National Air Traffic Controllers Association credited the Philadelphia team for maintaining safety through the radar and radio outage. "No controller starts their shift with the expectation that the equipment will fail them, but when it does they display professionalism and skill," the union said in a statement.

Who is backing the funding push?

The industry group Modern Skies Coalition endorsed Duffy's request again this week, arguing the recent outages "demonstrate how critical it is to replace the antiquated technology and outdated systems that underpin our nation's air traffic control infrastructure."

Robert Poole, who leads transportation research at the Reason Foundation he founded in the late 1970s, has long advocated removing air traffic control from the FAA entirely and funding it through ticket fees rather than annual congressional appropriations.

"We know what kind of technology is really needed to do that," Poole said, "but you can't do that on drips and drabs of annual appropriations."

Airlines were working through the backlog Tuesday as the FAA's line-replacement program continues. Whether Congress authorizes the full $20 billion Duffy has requested before another dual-line failure tests the system again remains the open question.