A glitch in air traffic control (ATC) systems software that forced the temporary closure of much of Irish airspace last Tuesday has been resolved.
The failure, which forced the shutdown of aircraft movements for a number of hours on Tuesday evening, has been described by the Irish Aviation Authority (IAA) as “an irregular software occurrence”.
Aviation chiefs were initially at a loss as to what caused the problem but the glitch was identified after “a thorough investigation of a technical issue” on the IAA’s primary ATC system in Ballycasey, Co Clare.
However, it remains unclear what caused the glitch or what measures have been taken to prevent a recurrence.”
The investigation involved technical experts and the system manufacturer whom the IAA said “worked tirelessly to identify the issue, research, isolate, and to resolve the matter”.
Over the course of Wednesday evening, the IAA switched back to its primary system from a back-up system. The IAA said its primary system “has been restored to full capacity”.
The areas affected by Tuesday’s shutdown were areas serviced by Shannon ATC, which includes Shannon Airport, Cork Airport, and transatlantic overflights, but not Dublin Airport, which has an independent system.
The IAA said once the fault was identified, a “comprehensive testing and safety analysis was carried out to ensure that the system was fit to return to operations”.
“The outcome of this was positive and accordingly operations were transferred back to the primary ATC system last night [Wednesday],” said the IAA.
The authority said when the fault occurred on Tuesday evening, it was “satisfied that the back-up system and contingency planning worked as required”.
It said the glitch was not a radar issue and involved “a module on our ATC system which affected the performance of this system”.
The IAA also said that the back-up system is a full replica of the IAA’s main ATC system and that this allowed it to provide a full and normal, safe ATC service once transfer to this system was completed.
The authority said regulatory procedures when transferring to the back-up system necessitated restrictions on traffic flow.
The flow rate was zero for a number of hours on Tuesday evening while the airspace was shut down.
Eurocontrol, the European Organisation for the Safety of Air Navigation, described the incident as a “radar failure” on its network operations portal but the IAA said it was not a radar issue.
The IAA’s Area Control Centre in Shannon handles more than 90% of all air traffic on the North Atlantic, approximately 1,400-1,500 aircraft every 24 hours during the busy summer months.
In 2017, Shannon Air Traffic Control safely handled more than 343,000 flights.