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The head of the UK's National Air Traffic Services said Wednesday that a cyberattack has been ruled out as the cause of a massive disruption at Heathrow Airport, the third major failure at the facility in three years. Airlines sharply criticized the organization over the incident, which caused widespread flight delays and cancellations. The disruption renews scrutiny of the resilience of UK air traffic infrastructure and raises questions about accountability for repeated system failures affecting one of the world's busiest airports.