A router swap gone wrong grounded US flights; officials rule out cyberattack

Behind Friday's nationwide stop of all flight departures (a ground stop) in the United States was a routine router replacement job, officials say. As contractor L3Harris replaced old, discontinued copper wire with new fibre optic lines, a router overloaded the air traffic control system and cut communications — and the country's airspace stayed shut for more than four hours.

The Federal Aviation Administration (FAA) ordered a nationwide ground stop of flights at 3:54pm East Coast time (20:54 GMT) on Friday, citing a telecommunications outage affecting air route traffic control centres. The stop was removed at 8:15pm on Friday (01:15 GMT on Saturday), but the knock-on effects continued: more than 5,000 flights were cancelled in the US on Saturday after over 9,000 were scrapped a day earlier. According to aviation analytics firm Cirium, hundreds of flights were still delayed or cancelled on the night the ground stop was lifted.

Transportation Secretary Sean Duffy said on Saturday that on Friday afternoon L3Harris was replacing a section of the system's old copper wire with new fibre optic lines in a remote location. The router in that location then started overloading the air traffic control system, causing communications disruptions. When officials could not locate the cause of the overload, they grounded flights nationwide.

Duffy said 'contractor error or a faulty piece of equipment' caused the router to start flooding other ones. 'We had 1,000 connection attempts every four to five seconds,' he told reporters. The issue affected communications at 17 of the FAA's 22 en route centres.

The Professional Aviation Safety Specialists (PASS), a union representing FAA safety employees, said the issue was isolated to two routers that were updated on Friday. An official told the Reuters news agency it was believed the routers were in Arkansas and Texas. An FAA official said the agency conducted a safety assessment before the work; the union said PASS-represented technicians were not involved in the upgrades that led to the ground stop.

The decision to suddenly ground all planes initially triggered speculation of a cyberattack, and White House officials convened an emergency meeting in the Situation Room on Friday. But the US government has since said it did not believe that was the cause. 'Once we were able to isolate the work being done at this location, all of our systems came back online,' Duffy said. 'So we don't believe this was cyber at all.' FAA Administrator Bryan Bedford said at Saturday's news conference: 'We see zero evidence of anything nefarious and zero evidence of anything AI-related.'

Aircraft already in the air were allowed to continue to their destinations and land during the ground stop, while international flights were handled on a case-by-case basis, with some allowed to depart despite the restrictions. About 4,000 aircraft were in US airspace when the stop was announced; despite limited radar and communications capacity, all of them landed safely.

The most dramatic moment of the chaos unfolded in the Texas sky. A student pilot on his first solo long-distance flight was left bewildered when he heard the news of the stop mid-air. According to Reuters, he had taken off from Hicks Airfield near Fort Worth, Texas. In conversation with the air traffic controller he said: 'Madam, I am a student pilot. To be honest, this is my first solo long-distance flight. I don't understand what I need to do.' Understanding the situation, the controller calmly guided him back, also telling him to avoid other aircraft including two helicopters in the air. The pilot asked, 'Is there a problem at Hicks Airfield?' The controller replied that there was no problem there. Step-by-step landing instructions followed, and according to flight tracking firm FlightAware, the pilot landed safely within a few minutes.

Flight cancellations and delays left thousands of passengers stranded at airports from Boston to Seattle and from New York to Los Angeles; many passengers looked for buses, trains and rental cars as alternatives. Tens of thousands of people remain stranded at airports across the country, while others have been left to pay surge prices for hotels and rental cars. Airlines have issued travel waivers for affected passengers to rebook flights for later dates at no cost.

Amid the chaos, passengers on one Southwest Airlines flight had an unusual experience. The Los Angeles-to-Orlando flight carried the bands Hoobastank, Simple Plan and The Used, and the singer Lolo. After news of the shutdown spread, the artists held a small concert inside the aircraft, performing through the plane's announcement system using a microphone and amplifier they had with them. Lolo later wrote on social media that passengers learned via Wi-Fi at 35,000 feet that air travel across the United States had been shut down.

Duffy said L3Harris, which has performed decades of work for the FAA, 'didn't meet the moment.' 'They own this network. They're our prime contractor. I can't go somewhere else. Frankly, we're going to hold people accountable,' he said. Whether it was installer error or a faulty router that was installed has not yet been determined, he added.

In response, L3Harris told Al Jazeera it has been working 'in close coordination with the FAA' and that safety and reliability are its 'highest priorities.' A spokesperson said: 'We are supporting the FAA in its investigation to understand the conditions that led to the November 13 ground stop of our nation's air travel.' L3Harris said it has been modernising the communications infrastructure supporting the National Airspace System and has completed more than 70 percent of the planned conversion from legacy copper wires to a fibre optic system. According to the US Department of Transportation, L3Harris is the contractor behind the systems upgrade; The New York Times reported that three-fourths of the company's revenue comes from US government contracts, largely from the military. The FAA said it was doing additional testing with L3Harris to see if there are any further risks.

Ageing technology and equipment alongside a shortage of several thousand controllers have long been concerns plaguing the US air traffic control system, officials say. Duffy on Friday called for $50bn in funding to upgrade these systems, up from his earlier request of $30bn, after Congress approved $12.5bn last year. 'When we see that, your safety is paramount. We shut down the airspace,' Duffy said.

It was the longest and only second nationwide stop of flights in the United States since the attacks of 9/11 in 2001. Bedford cautioned that returning to normal could take time: 'We have crews and aircraft that are out of position for 12,000 flights that were lost. These crews, pilots and flight attendants need to get to their points of reconnection with their schedules.' He stated that he thinks 'the worst is behind us.' Duffy said airlines were expected to restore their full schedules by Sunday night.