An air ambulance service is to be stood down for part of the winter period over staffing issues.
The Emergency Aeromedical Service (EAS) has been running since 2012 without interruption.
It has operated out of Custume Barracks in Athlone.
But the Defence Forces says the Air Corps will not be in a position to run the service for four days per month for a period of four months.
This starts in November and ends in February 2020.
During those 16 days, the Irish Coast Guard will provide reserve cover to the National Ambulance Service.
It says this is line with a 2015 Government decision establishing the service.
The Defence Forces says: "The Irish Community Rapid Response (ICRR) charity Helicopter Emergency Medical Service (HEMS) based in the south of the country will continue to be available and the potential for it to provide increased support is also being explored.
"The priority is to provide the best service possible using all available resources during the four day periods each month when the Air Corps are not available for EAS taskings.
"This interruption is regrettable but necessary from a safety and governance perspective."
Fianna Fáil's defence spokesperson, Jack Chambers, says lives are being put at risk.
"The Minister for Defence must clarify reports that the Emergency Aeromedical Service in Athlone is being stood down for 16 days over the winter due to a shortage of pilots spread between now and February.
"This is extremely concerning for the regions which rely on this service to save lives.
"What are the contingency arrangements in place for people who may need medical attention?
"The Emergency Aeromedical Service... has been one of the areas hit hardest by the recruitment and retention crisis affecting the Defence Forces.
"The reported suspension of the air ambulance is completely unacceptable and poses a real risk to the lives of people within the locality.
"Like the docked naval ships, this is the outcome of the recruitment and retention crisis which Minister Kehoe continues to ignore.
"Structures in our defence forces are collapsing and the exodus of personnel is accelerating".