The family of Dara Fitzpatrick, who lost her life in the Rescue 116 crash, say they were badly let down by the operator CHC.
They hope a report by the AAIU into the incident, will ensure those responsible will urgently implement the necessary changes to ensure such an accident will never happen again.
Dara Fitzpatrick, Mark Duffy, Paul Ormsby and Ciaran Smith all lost their lives in the crash off the Mayo coast almost five years ago.
The report by the Air Accident Investigation Unit found they were unaware a lighthouse and terrain were on the flightpath, as neither databases nor imagery detected it.
Security auditor Retired Lt Col Kevin Byrne says there was nothing to warn them of the danger ahead.