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/

Air traffic chaos caused by 'one in 15 million' event

The UK's air traffic control system shut itself down after software confusion over an unusual flight path.

BBC News
UK air traffic woes caused by 'invalid flight plan data'

Former BA boss slams resilience, says explanation 'doesn't stand up from what I know of the system'

The Register