The Oireachtas Transport Committee has heard from Aer Lingus regarding the technical failure on September 10th that impacted 32,000 passengers.
The complete failure of IT systems brought Aer Lingus flight activity to a standstill.
It later emerged that the fault lay with a fiber-optic cable in the UK, which was damaged as a result of construction work.
7,500 applications for compensation have been made to the airline. 91% of applications for compensation have been processed and that the remaining 700 applications should be processed by the end of the month.
Aer Lingus would not say how much money has been paid out in compensation and refunds but that it was in the millions of euro.
Of the 32,000 passengers who were impacted, 21,000 of them were delayed and 11,000 had their flights cancelled.
Tipperary TD Michael Lowry, a committee member, described the day as a shambles and said passengers got a poor response in the days following the mass cancellations.
Ms. Lynne Embleton, CEO of Aer Lingus, agreed with Deputy Lowry that the scale of the problem was phenomenal, but added that it was an exceptional event with the main system failing and the back-up system also failing.
A new layer of monitoring has now been installed to prevent a recurrence.
Aer Lingus says they have to rely on a UK provider as the service they need is not available in Ireland as of now.
