It's emerged the Air Corps was initially asked to embark on the mission Rescue 116 was sent on.
The Defence Forces confirmed to Newstalk how Rescue 116 ended up on the operation.
The Irish Air Corps received a request from the coast guard to provide top cover for a evacuation off the west coast.
They weren't able to provide this outside of normal hours, so the Rescue 116 helicopter was then sent on the mission instead.
The Defence Forces say at 1.45am they then received an emergency request to conduct a search for the helicopter, which had gone missing.
The Air Corps have noted plans are in place to deal with the shortage in personnel, however it meant they were unable to provide cover the night Rescue 116 was dispatched.