Airline schedules could be disrupted for days after all US flights grounded for hours

All departing US flights had been grounded after the Federal Aviation Authority (FAA) issued a nationwide order on Friday, citing “extraordinary ​circumstance and reasons of safety".Airports were thrown into chaos after a communications failure at air traffic control centres.More than 6,600 flights were cancelled and 8,600 delayed, with another 1,500 already cancelled for Sunday, according to Flightradar24. Aviation analysts said the four-hour nationwide grounding could disrupt airline ⁠schedules for days. It was the longest flight shutdown since the attacks of September 11th, 2001. READ MOREThe FAA lifted the ground stop later on Friday, with transportation secretary Sean Duffy saying US airspace reopened at 8.15pm ET (1:15am GMT). But departures would ⁠resume gradually, and it would take ​time for airlines to restore normal operations, he warned. “It’s going to be slow.” All US-bound departures from European airports were suspended until 5am UTC on Saturday, according to a notice published by the European traffic control agency, Eurocontrol. US airlines, including American, United and Southwest, began resuming flights on Friday night. “Thank you for your understanding as we work as quickly as possible to fully restore normal operations,” Delta said. Duffy said the federal government had “identified the problem” that brought down the US air traffic control system on Friday, and it was “operational right now”. The system was “incredibly old”, he said. “Our routers actually got overloaded with data, and ... they started to give us inconsistency in the data from those routers. And because of that, we shut the system down.” There was no indication from preliminary investigations that the communications stoppage was tied to a “nefarious attack”, homeland security secretary Markwayne Mullin said. Duffy blamed Congress for failing to fund a new air traffic control system that he said could prevent such outages, and called for $50 billion to modernise it.Shortly before the announcement that flights were grounded, ‌the ‌FAA ​halted traffic in Chicago due to air traffic control communications issues. ⁠The agency said: “All ​departing traffic should remain ​'groundstopped’ until further notice.” The FAA said international ‌flights will be managed on ​a case-by-case basis.The FAA advised all airborne flights to circle instead of landing during the communications outage. It told pilots to circle along predetermined routes instead of landing due to “equipment outages”.There is a “possibility” that both arriving and departing flights between Dublin Airport and the US could be impacted on Saturday morning due to the ground stop, an airport spokesman said on Friday night.“We are aware of the current suspension of flights departing from the United States,” Graeme McQueen, spokesman for Dublin Airport, said. “It remains unclear how long this suspension will remain in effect, and there is a possibility that it could impact both arriving and departing flights between Dublin Airport and the United States on Saturday morning.”A total of 24 flights from the US were due to land at Dublin Airport before 10.30am on Saturday, with the first of those, from Boston, scheduled to arrive at 4.15am.“Passengers are advised to contact their airline directly for the latest updates on the status of their flight,” he said.Markwayne Mullin, the department of homeland security director, said at a news conference that preliminary investigations into the stoppage do not indicate that it was tied to a “nefarious attack”.“There’s no indication as of yet that this was a nefarious attack against it. It’s just a telecommunications outage as of right now,” he told reporters.After restoring communications so all airborne flights can land, Mullin said “we’re going to continue to work to find out what the root of the cause is”.“We’re not ruling out anything at this point,” Mullin added.The government has been working to overhaul the outdated technology that air traffic controllers rely on since Congress approved $12.5 billion for the project last year.Miles of old copper wires have been replaced with fibre optic lines and old radio systems are gradually being replaced at airports across the country.But much work remains. Duffy has said that another $30 billion will be needed to complete the work, and the White House has begun lobbying Congress to approve it.The problem appeared similar to a regional air traffic control communication outage in September that snarled hundreds of flights across the northeast, aviation safety expert Steve Arroyo said, except this time on a nationwide scale.It may be linked to the outdated technology used by air traffic controllers.“If you don’t have that ability, whether it’s because the old wires that they have are just run down or for whatever reason, you’ve got to stop airplanes on the ground,” said Arroyo, a former United Airlines pilot. “And not put them in the air where you’re going to risk not being able to communicate with them.”The FAA has more than 14,000 air traffic controllers who handle the more than 44,000 flights that take off from airports across the US each day, according to FAA data.Friday was the second groundstop of all departures in the US since the September 11th, 2001, attacks. The other happened in January 2023, when the FAA paused all domestic departures for less than two ‌hours. Additional reporting by Guardian/Reuters