In August, the UK was hit by a major technical failure in air traffic. No flights were coming in or out of the UK and more than 1,500 flights were cancelled. 

A preliminary report investigating the accident was presented today. The problem turned out to be a technical fault, which only happens once in 15 million, Skynews reports.

Two identical but separate markers on the flight system are said to have caused the problems. The error led to both the primary system and the backup system entering a ”fail-safe mode.”.

Source: Aftonbladet.se