Everyone is reporting on "Air traffic chaos caused by 'one in 15 million' event". https://www.bbc.co.uk/news/business-66723586

But the report says "This scenario had never been encountered before, with the system having previously processed more than 15 million flight plans" https://www.nats.aero/news/nats-report-into-air-traffic-control-incident-details-root-cause-and-solution-implemented/