On the 28th August the UK's air traffic control system to shut down, causing hundreds of flights to be delayed or cancelled. Before now the shutdown was blamed on a vague data processing glitch, but the exact cause has now been disclosed.
In its initial report published on Wednesday, [the National Air Traffic Service] said that at 08:32 on 28 August, its system received details of a flight which was due to cross UK airspace later that day.
The system detected that two markers along the planned route had the same name - even though they were in different places. As a result, it could not understand the UK portion of the flight plan.
This triggered the system to automatically stop working for safety reasons, so that no incorrect information was passed to [the National Air Traffic Service's] air traffic controllers. The backup system then did the same thing.
Martin Rolfe, chief executive of [the National Air Traffic Service], said that the system did "what it was designed to do, i.e. fail safely when it receives data that it can't process".