A JetBlue plane takes off from Ronald Reagan Washington National Airport after the US Federal Aviation Administration lifted a national ground stop, in Washington, DC. (Reuters image)NEW DELHI: Air travel across the United States is expected to take until late Sunday to return to normal after a nationwide flight disruption caused by communication failures at air traffic control centres. The Federal Aviation Administration (FAA) has traced the problem to maintenance work involving a telecommunications network and a potentially faulty router installed by its contractor, L3Harris, officials said on Saturday.The disruption continued to affect thousands of passengers even after the FAA lifted its nationwide ground stop on Friday evening. As of 6:45 pm ET (23:45 GMT) on Saturday, airlines had cancelled more than 6,150 flights and delayed over 7,300, according to flight-tracking website FlightAware. More than 530 flights scheduled for Sunday had also been cancelled.The disruption followed an even worse day on Friday, when airlines cancelled around 9,200 flights and delayed 7,500 after the FAA ordered a nationwide ground stop that halted nearly all departing flights for almost five hours.FAA chief Bryan Bedford said he expected airline operations to largely return to normal by late Sunday. He apologised to passengers and said the system remained stable.The Friday shutdown was the longest nationwide halt to US air travel since the September 11, 2001, attacks and one of the worst single-day disruptions for the country's aviation sector.Maintenance work and router failure under investigationTransportation secretary Sean Duffy said the disruption may have been triggered by routine maintenance work carried out by FAA contractor L3Harris at a remote facility. The work involved switching telecommunications lines from older copper wiring to fibre-optic infrastructure.Duffy said officials were investigating whether the disruption resulted from an error by the contractor or a faulty router installed during the process."We're working to determine whether we had incompetence, meaning was it user error or installer error from L3Harris, or did they install a faulty router? We haven't determined what the fault was," Duffy told reporters at a news conference.He also questioned the contractor's role in maintaining the network.“Which begs the question for us: What did L3Harris do? Did they make mistakes yesterday?” Duffy told reporters. “They own this network. They’re our prime contractor. I can’t go somewhere else. They own it. Or was it a faulty router? And we’re going to find that out. And frankly, we’re going to hold people accountable.”Duffy described the maintenance work as a routine procedure that had been carried out across the country for decades. He said around 30% of the older copper wiring in the system was yet to be replaced, with officials working to identify the remaining locations.L3Harris said it was cooperating with the FAA's investigation.“L3Harris has been modernizing the communications infrastructure supporting the National Airspace System in close coordination with the FAA,” the contractor said in a statement. “We are supporting the FAA in its investigation to understand the conditions that led to the Nov. 13 ground stop of our nation’s air travel. L3Harris takes the nationwide ground stop and its impact on travelers, airlines and air traffic operations seriously.”Communication failures affected 17 of 22 air traffic control centresDuffy said the trouble began on Friday afternoon when air traffic control centres experienced instability in radar and communication systems. The router issue allegedly caused data overload at other communication centres, affecting their ability to exchange information."We had over 1,000 connection attempts every four to five seconds, and what that did was (it) gave us issues with our communication with airplanes, and it also caused some disruption with our radar," Duffy added.The disruption affected 17 of the FAA's 22 en route air traffic control centres, which manage aircraft during the cruising portion of their flights.Bedford said the FAA ordered the nationwide ground stop after receiving reports of communication frequencies going in and out at multiple facilities. Controllers had to switch between primary and backup systems, while officials struggled to establish the extent of the problem.He said the decision was taken as a precaution because of the number of facilities reporting disruptions.“If that had been a single facility, we would have just worked through it,” Bedford said.He added: “But when we saw it go to two, three, 10, 17 facilities, that’s when we started to realize there was something much larger going on here.”Bedford clarified that none of the affected facilities completely lost communication systems."No facilities went dark. Nothing was fully lost," Bedford added.The FAA said it was conducting additional tests with L3Harris to determine whether any further risks remained.Officials rule out cyberattack as causeThe disruption prompted the White House to convene an emergency meeting in the Situation Room on Friday as federal agencies examined whether the failure could have been caused by a cyberattack or deliberate interference.However, Duffy and Bedford said there was no evidence to suggest that the incident was linked to a cyberattack or any other malicious activity.“A lot of questions came in yesterday. ‘Was this a, a cyber attack? Did some foreign nation attack this network?’ And the answer to that is we don’t believe so,” Duffy said.Bedford later added: “We see zero evidence of anything nefarious, and zero evidence of anything AI-related.”Airlines cancel thousands of flights as disruption continuesAlthough the FAA lifted the ground stop on Friday evening, the disruption continued as airlines struggled to reposition aircraft, flight crews and other personnel to resume regular operations.Delta Air Lines, United Airlines and American Airlines each cancelled around 25% of their flights on Saturday, while JetBlue cancelled nearly 45%, according to the report. Airlines also issued travel waivers allowing passengers to rebook flights for later dates without additional charges.The disruption left thousands of passengers stranded at airports and affected travel plans across the country. Some college football teams were also stranded on Friday, ahead of matches scheduled for Saturday.Bedford said he believed the worst of the disruption was over, but warned that the country's ageing aviation infrastructure remained vulnerable to further failures.“I do think the worst is behind us,” Bedford said, adding that the FAA expected a full recovery by Sunday ahead of a busy travel period leading up to the Thanksgiving holiday.He cautioned that the ageing technology would remain a concern until it was replaced, saying the FAA would continue investing in keeping the system operational.Duffy seeks $50 billion to upgrade air traffic control systemThe disruption has renewed concerns over the condition of the US air traffic control network, which has been affected by ageing equipment, communication failures and a shortage of several thousand air traffic controllers.Duffy called for $50 billion in additional funding to modernise the system, raising his earlier request of $30 billion. Congress had approved $12.5 billion for upgrades last year.“I think this is a sign for them to lean in,” Duffy said. “Let’s make the investments and look forward to a brighter future in aviation, a safer future, a more efficient future in aviation.”House Speaker Mike Johnson said on Saturday that he supported additional funding for the FAA and that Republicans would use their remaining time in the congressional majority to push for the investment.“We don’t really need any investigation to understand we need further investment,” Johnson said, “We’re going to work to get it done.”Republicans control Congress until next year, when Democrats are set to take over following their gains in the November 3 midterm elections.Join conversationShare your thoughts in the commentsBe respectful · TOI community guidelinesUS Representatives Rick Larsen and Andre Carson, Democrats expected to lead the House Transportation and Infrastructure Committee and its aviation subcommittee next year, said their panels would examine the disruption.In a joint statement on Saturday, they said their panels would "hold the administration accountable for what happened to make sure this chaos does not happen again."Larsen and Carson also said the Transportation Department had awarded contracts worth $4.3 billion since receiving the $12.5 billion allocation last year, but had spent only $1 billion so far.You use AI every day. 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