The Irish Aviation Authority (IAA) has a joint venture agreement with the manufacturer of the Eurocat aircraft traffic control system, which crashed at Dublin airport last week, that is designed to promote its use at European airports.

Eamonn Brennan, chief executive of the IAA, agreed the joint venture with Thales ATM, a French air traffic equipment provider, in 2006. This was three years after paying €90m to have the Eurocat system installed in Ireland.

The joint venture includes the Swedish-based LFV Group and Danish-based Naviair. The three paid Thales an undisclosed sum for upgrades to the system that would also be made available to new Eurocat customers.

According to an aviation source, one of the aims of the joint venture, known as COOPANS, is to encourage the use of Eurocat at more European airports.

Thales describes the Eurocat system as “the industry standard” with demonstrable benefits from a “proven operational track record”.

Since last Wednesday’s shut-down of air traffic control at Dublin airport a team of engineers from Thales and Hewlett-Packard, the software company, have been monitoring the system. According to Lilian Cassin of the IAA, the source of the problem was a faulty piece of hardware which has been replaced. She was unable to say what type of hardware was involved, but it meant that information on some airplanes was not available to air traffic controllers.

The problem had occurred for brief periods on four occasions over the last month, she said. When it re-occurred twice last Wednesday for separate periods of 30 minutes, the IAA decided to shut the system down.

Kieran Daly, editor of UK-based Air Transport Intelligence magazine, said he believed that the problem as described by the IAA suggested that a software problem was the issue. “A software problem would be much more complex to resolve,” he said. A hardware problem could be caused by something as basic as water dripping from a roof onto a computer or a rat chewing a cable.

According to an air traffic controller at Dublin airport who did not want to be identified, staff had taken a long time to become familiar with the system and are still learning. “As far as I’m concerned, a system like this should have no more than five minutes of downtime a year so someone needs to explain to Dublin controllers what’s been going on and assure us that it won't happen again,” he said. “Otherwise the system will not regain our confidence.”

Cassin refused to be drawn on who had responsibility for the faulty equipment. “We’re not entering into a blame game,” she said. “We are not even considering the issue of compensation at the moment.”

A spokeswoman for Thales said she “assumed” her company had responsibility for the entire product. She said that Thales and the IAA were jointly responsible for maintenance of the system which had not failed at any other airport. Thales has contacted its other customers to inform them of the problem.

Disruption to flights at Dublin airport has eased considerably but will continue into next week because Eurocat is still operating at reduced capacity. The disruption has prompted Michael O’Leary, chief executive of Ryanair, to call for the dismissal of Cathal Guiomard, the aviation regulator. O’Leary said the delays had cost Ryanair ¤1m a day.

Air passengers experienced only slight delays at Dublin yesterday. Some transatlantic arrivals were well behind schedule. One flight from Orlando, which was due to arrive at 3am, landed nine hours late.

About 250 people who were stranded in Cyprus after tour operator Failte Travel went bust were due to return last night. The holidaymakers were left without an aircraft at Larnaca after the Dublin travel company announced that it had ceased trading.

The Commission for Aviation Regulation assisted efforts to get the group back to Ireland, after two flights were cancelled on Friday. The commission said it was seeking an aircraft to get those stranded home by last night.

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