Systems crashed causing 1,500 flights to be cancelled, leaving thousands of passengers stranded abroad.
The technical glitch which caused last week’s flight chaos in the UK was a “one in 15 million” event, according to air traffic service NATS.
On 28 August, thousands of passengers were left stranded after 1,500 flights were cancelled during one the busiest parts of the summer season.
The service says the chaos was caused by a single flight plan that wasn’t properly processed by part of its system, causing it to shut down automatically within a matter of seconds.
A report released by NATs outlines how this extremely rare error occurred.
The UK’s National Air Traffic Services (NATS) has confirmed the root cause of the meltdown in the preliminary report released today.
The report from NATS found that one flight plan with two identically named but separate waypoint markers outside of UK airspace was behind the technical glitch.
These waypoints, which represent locations along an aircraft’s route, are identified by a series of letters and numbers. The two identical points in the problem flight plan were 4,000 nautical miles (7,408 km) apart but shared exactly the same name, forcing the system to stop working for safety reasons.
“In these circumstances, the system could not reject the flight plan without a clear understanding of what possible impact it may have had. Nor could it be allowed through and risk presenting air traffic controllers with incorrect safety-critical information,” NATS said.
A backup system also failed and no correct information was sent to air traffic controllers. This series of events unfolded in just 20 seconds.
It meant that the service couldn’t process flight plans automatically for several hours and instead had to switch to a slower, manual process. The number of plans NATS could handle dropped from 400 per hour to as low as just 60, causing more than a quarter of flights to be cancelled.