Investigators have said an “irregular software occurrence” caused an air traffic control system failure on Tuesday night, which led to the temporary closure of parts of the Irish airspace.
The issue affected the Air Traffic Control (ATC) hub in Ballycasey, Co Galway which provides air traffic control for Shannon and Cork Airports, as well as transatlantic flights.
The issue led to disruption to flights to and from these airports.
Following a detailed review of the problem the Irish Aviation Authority (IAA) on Thursday said the technical failure was not a radar fault, and related to "a module on our ATC system."
A spokesman said in simple terms the “glitch” discovered in the system software had to be isolated and fixed.
In a statement, the IAA said full radar coverage of Irish skies had been maintained throughout the incident.
Flights already in the air when the system went down were in no danger, and were transferred immediately onto a back-up ATC system, the authority said.
A small number of flights were delayed on Tuesday night, as a safety precaution.The issue did not affect Dublin Airport, which operates an independent system.
Several flights due to land in Cork and Shannon Airports were redirected, some to Dublin. A number of flights due to take off from both airports were delayed while the issue was initially investigated.
The software glitch was “unique” and technicians had not come across it before, the spokesman said.
The software fault has been “identified and isolated,” the authority said. Technical experts and software manufacturers were brought in to trace the source of the problem.
“When this was completed, 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,” the authority said.
Following this air traffic control operations were transferred back to the primary system.
Safety procedure for switching to the contingency system required air traffic to be restricted on Tuesday evening, the authority said.
