The Irish Coast Guard helicopter which crashed on a rescue mission early Tuesday had been tasked to the scene after the Defence Forces had been unable to provide assistance.
In a statement, the Defence Forces said it did not have the capacity to provide support because of a loss of experienced personnel in both air crew and air traffic control.
Minister with Responsibility for Defence Paul Kehoe admitted "challenges have arisen in relation to the recruitment and retention of personnel in particular areas of expertise".
According to the latest figures , as of November 30th, 2015, the Irish Air Corps had 750 personnel, some 136 short of its "stabilised strength" of 886, the number needed to carry out all existing functions.
Mr Kehoe said the reduction in the capacity of the Air Corps was notified during last summer to the agencies with which the Department of Defence has service level agreements for the provision of support. These include the Coast Guard and the Department of Health. The Irish Air Corps regularly air-lifts passengers between Irish hospitals and sometimes to the UK.
The Irish Air Corps was asked to provide support at 10.06 pm on Monday to a rescue mission off the coast off Co Mayo.
A fisherman working on board the international blue whiting fleet 250km west of the Mayo coast had been injured and required medical evacuation to hospital.
The request was made for the CASA CN-235, the maritime patrol aircraft commonly used in such search and rescue operations, to provide “top cover” to an Irish Coast Guard aircraft in Sligo which had been flying out to the British-registered fishing vessel.
The request was refused because there was a lack of experienced personnel available so Rescue 116, the helicopter based in Dublin, was subsequently deployed to Co Mayo where it crashed into the sea.
The Defence Forces said there has been a service level agreement between the Department of Defence and the Department of Transport, Tourism and Sport for the mutual provision of services between the Air Corps and the Irish Coast Guard since September 2013.
That agreement provided for top cover on an “as available basis. Availability is determined having regard to crew availability, aircraft availability, weather conditions etc.”
The Rescue 116 Sikorsky helicopter got into trouble close to the westerly lighthouse at Blacksod. It was turning in from sea to make an approach at the lighthouse for a routine refuel when it disappeared.
Though the Casa CN235 was not available at 10.06pm, it was made available at 1.45am when the Irish Air Corps was alerted to the fact that a helicopter had gone missing. The Casa departed Casement Aerodrome at 4.24am.
The Defence Forces statement said steps were underway to remedy the shortage of personnel in the Irish Air Corps.
Currently there are 28 cadets, in three classes, undergoing the various stages of the Air Corps cadetship to become pilots. Of these, eight Air Corps cadets are in the final stages of their training with commissioning of these cadets likely to take place in the last quarter of the year.
The statement concluded: “Air traffic control training is also taking place and options to ensure the longer-term sustainability of air traffic control services in Baldonnel are being identified.”
In a series of parliamentary questions to independent TD Tommy Broughan, Mr Kehoe revealed the Irish Air Corps is 173 personnel or 20 per cent lower than the establishment figure (preferred figure) as set out in the Defence Forces Regulations of 887. There were 26 vacancies for pilot officers as of December 31st, 2016.
The Irish Air Corps is seeking to bolster numbers with 28 cadets in three classes undergoing the various stages of the Air Corps cadetship to become pilots.
Security specialist Declan Power told Newstalk there had been "a gradual erosion of the capacity to respond".
“All the elements of this story must be very disturbing for the families.”
He said: “You can’t just recruit overnight. It takes two to five years to get somebody to the standard of being a pilot of a Casa, or to be an air traffic control officer, or various other specialisms that exist within the Air Corps.”