The UK Civil Aviation Authority is launching an independent review into the NATS technical issue that occurred on Monday 28 August, causing hundreds of flights to be delayed or cancelled.
Following this significant disruption, NATS has provided the Civil Aviation Authority with a preliminary investigation report on the issue, which sets out its causes and details the actions taken to rectify and mitigate the effects.
The report identified a fault with a flight plan processing sub-system called Flight Plan Reception Suite Automated – Replacement (FPRSA-R). The system encountered a rare set of circumstances with a flight plan that included two identically named, but separate waypoint markers outside of UK airspace.
This led to a ‘critical exception’ where both the primary system and its backup entered a fail-safe mode.
The system was then unable to reject or accept the flight plan without a clear understanding of its impact, as this would have risked presenting air traffic controllers with incorrect safety critical information.
It therefore took time to manually identify the problemand the specific data and to then isolate and remove it in a controlled way.
This is the first time that this scenario has been encountered, with the system having previously processed more than 15 million flight plans over 5 years. The report states that steps have now been taken to ensure the incident cannot be repeated.
“Keeping the sky safe is what guides every action we take, and that was our priority during last week’s incident. I would like to reiterate my apology for the effects it had on so many people, including our airline and airport customers. Incidents like this are extremely rare and we have put measures in place to ensure it does not happen again.
“Our preliminary report, provided to the CAA this week, details what caused the incident, how we responded and the steps already taken to prevent recurrence. We welcome any further review of the incident that the CAA wishes to conduct.”
The UK Civil Aviation Authority will now conduct an independent review on the wider issues around the system failure and how NATS responded to it.
If evidence emerges to suggest that NATS may have breached its statutory and licensing obligations, the UK Civil Aviation Authority will take any appropriate steps.
The review will also determine lessons to be learned for the future.
“Millions of passengers every year rely on air traffic control to work smoothly and safely. The initial report by NATS raises several important questions and as the regulator we want to make sure these are answered for passengers and industry.”
Details of the independent review will be published by the end of September 2023.
