Taoiseach Enda Kenny has said that it is "well known" that the Air Corps has lost personnel but the Coast Guard is "generally in a position" to provide cover it requires.
Mr Kenny was speaking in Washington DC where he is attending St Patrick's Day events.
He was responding to confirmation from the Defence Forces that a request for Air Corps support by the Coast Guard on Monday night was denied due to a lack of experienced personnel.
The Taoiseach was asked if there is a shortage of personnel in providing rescue support.
He said: "It's well known the Air Corps have lost personnel, air traffic controllers. So they have an arrangement with the Air Corps that where crews are available "top cover" is provided.
"But the Coast Guard generally are in a position to do that themselves and in this case 'top cover' was provided by one of their own helicopters."
Earlier the Defence Forces confirmed a request for it to provide top cover in the mission Coast Guard Rescue 116 subsequently crashed on, was logged at 10.06pm on Monday.
However the Air Corps was not able to carry out the mission as its fixed-wing aircraft was unavailable.
The request was denied due to the fact it was outside normal hours and there was a lack of "experienced personnel" available.
Top Cover means observing a mission and providing support
The Department of Defence has said that in 2017, three requests for top cover, including the initial one logged by the Air Corps on 13 March, could not be responded to due to reduced availability.
The Air Corps has 15 fixed wing aircraft, two of which are CASA CN235.
Only the CASA CN235 has the necessary equipment and capability to conduct top cover operations.
The minimum number of personnel required to launch a CASA CN235 aircraft is 12, across a range of specialities.
The CASA CN235 primary undertaking is maritime surveillance and fishery protection, however it can undertake a range of other roles in addition, some of which are: Air Ambulance, Pollution Patrol, Customs Co-operation and Assistance, Search and Rescue, Troop Transport and International Airlift (Logistics Support).
Minister with Responsibility for Defence Paul Kehoe said that as with other areas of the public service, challenges have arisen in relation to the recruitment and retention of personnel in particular areas of expertise.
Mr Kehoe said the reduction in the capacity of the Air Corps was notified last summer to the agencies the Department of Defence has agreements with for the provision of support.
He said moves to address the shortages in personnel being experienced by the Air Corps are under way with 28 cadets being trained to become Air Corps pilots.
Air traffic control training is also taking place and options to ensure the longer-term sustainability of these services in Baldonnel are being identified, he said.
Meanwhile, poor weather conditions off the west coast have hampered efforts to locate the black box flight recorder from the missing helicopter.
The main focus of the search operation is to locate three missing crew: Captain Mark Duffy, winch operator Paul Ormsby and winchman Ciarán Smith.
A fourth crew member, Captain Dara Fitzpatrick, was recovered from the water off the Mayo coast on Tuesday morning but pronounced dead a short time later.