Aging routers trigger five-hour US flight grounding before Thanksgiving

US departures resumed at 8:15pm Eastern Time on Friday after technicians restored the failed systems, but the damage was already done. Nearly 10,000 flights were cancelled during the disruption, according to flight-tracking site Flightradar24, and some aircraft at major airports sat waiting more than five hours for a gate. Airlines are now warning it could take days to clear the backlog of delayed and cancelled services.

The carrier tally is brutal: more than 2,200 cancellations each at Delta Air Lines and American Airlines, and 1,800 at United Airlines, Flightradar24 reported. The timing could hardly be worse. Industry group Airlines for America forecasts nearly 29 million passengers will fly on US airlines between November 20 and 30, and the grounding landed less than a week before that Thanksgiving rush.

Transportation Secretary Sean Duffy pointed the finger at tired hardware, saying aging routers had become overloaded with data and caused inconsistencies in the air traffic control system. He described an outdated system where the old hardware simply went down. Stranded passengers won't get compensation from the airlines either, because the failure hit the Federal Aviation Administration's systems rather than the carriers.

The freeze spilled far beyond US borders. European aviation authorities were asked to suspend US-bound departures during the emergency, and a small number of Australian flights were affected, with airlines working through their own backlog. The Australian Travel Industry Association warned disruption to domestic US flights could last at least 24 hours, and told Australians flying within the next 72 hours to contact their airline or travel agent if they hadn't received an update.

Friday's shutdown was the longest nationwide grounding of US flight departures since the September 11 attacks in 2001, and only the second nationwide groundstop since then, after a computer system failure in January 2023 halted domestic departures for about 90 minutes. Homeland Security Secretary Markwayne Mullin said there was no evidence of a cyber-attack and moved to reassure passengers about the safety of air travel.