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LONDON, Sept 18: British air traffic control operator NATS said on Friday an outage which affected hundreds of thousands of \u200bpassengers last week was cause by a software defect.<\/strong><\/p>\n The incident led \u200cto 2,000 flight cancellations and days of disruption, costing airlines millions of pounds as they scrambled to get crews and aircraft back in place and refund passengers.<\/p>\n NATS CEO Martin \u200bRolfe said the shutdown was not related to a problem in 2023 \u200bwhich also caused widespread disruption, nor was it linked to military \u2060intervention \u2013 as reported by some media outlets last week. He added that \u200bsafety was at no point compromised during the incident.<\/p>\n \u201cThis was a software issue \u200bin a specific part of our flight data system, that we have traced to a small subsection of coding,\u201d he said. \u201cThe issue has been identified and mitigation is in place \u200bwhile a permanent fix is safety tested and deployed.\u201d<\/p>\n Transport minister Heidi Alexander, who had \u200blast week demanded NATS produce a report on the matter and also ordered an independent \u200creview \u2060by the Civil Aviation Authority, said the disruption was \u201ccompletely unacceptable\u201d.<\/p>\n \u201cWe need to urgently understand why this issue was not discovered and fixed before it caused chaos,\u201d she said in a statement. \u201cIt is crucial that our national infrastructure is fit for \u200bthe future.\u201d<\/p>\n The incident \u200bfollowed a shutdown \u2060in August 2023 which caused travel chaos, costing airlines \u00a3100 million ($136 million). A smaller technical issue which NATS was behind \u200bin July 2025 also caused 150 cancellations.<\/p>\n Ryanair, Europe\u2019s biggest airline, \u200bhas repeatedly \u2060for Rolfe to resign since the 2023 failure.<\/p>\n The NATS report on the latest incident was triggered by a request for an identification code from an aircraft being \u2060followed \u200bby a request for a higher priority activity, \u200bpausing the first request.<\/p>\n \u201cHad the higher-priority request arrived even one millisecond earlier or later, the update would \u200bhave completed normally,\u201d the report said.<\/p>\n<\/div>\n