The Department of Transport's aviation security division is investigating a possible breach of security procedures aboard a flight to Shannon from London earlier this month.
The inquiry relates to an incident on August 12th when, contrary to security regulations, luggage was brought on a flight from Heathrow without the owner being aboard.
Aer Lingus today confirmed it had completed an internal investigation and passed its findings onto the department.
In a short statement issued today, the company said: "Aer Lingus is satisfied with the outcome of this investigation and has made a formal report to the Aviation Security Division of the Irish Department of Transport."
It is understood the incident occurred when an elderly lady checked in at Heathrow but missed her flight because she did not hear the final boarding announcement.