Four aircraft that cost almost €50million, used for vital medical evacuations and surveillance by the security forces, were grounded as they have not been properly maintained by the Air Corps, the Irish Mail on Sunday can reveal.

The Department of Defence and Defence Forces were unable to say last night when the Swiss-made Pilatus PC-12s – delivered just six years ago – will be back in operation. 

They are often used as air ambulances for emergency medical evacuations and to do sensitive surveillance work for the gardaí, the Army and the Naval Service.

A source told the MoS: ‘The aircraft have been operating out of Baldonnel [Air Corps headquarters at Casement Aerodrome] for the past six years… They all had to be grounded last week.

‘They were grounded after a manual check was done on them and it showed more or less that the planes had not been properly maintained.

‘Before the check, they had been using a computer for maintenance and that showed that everything was okay. 

'It was not until the manual check that the problem was found. 

'So the question now is – even though the planes have safety certificates – does this mean they were safe to fly?’

The Defence Forces this weekend confirmed the fleet has been grounded at Baldonnel, and that there are maintenance problems.

The Defence Forces insisted the planes have valid safety certificates. 

But a spokesman would not say if arrangements have been made for medical evacuations and surveillance during the grounding.

In a statement, the Defence Forces said: ‘Óglaigh na hÉireann does not comment on the disposition of our Air Corps Fleet for reasons of operational security. 

'We took delivery of the Pilatus PC-12 aircraft in April 2020. 

'They hold current Military Airworthiness Review Certificates issued September 2025, valid until September 2026. 

'However the current pause is a maintenance scheduling matter, not a certification issue.

‘In line with best practices, the Air Corps carries out scheduled maintenance on the PC-12 fleet at intervals prescribed by the manufacturer, all scheduled through a Maintenance Information System.

‘A routine review by Air Corps aeronautical engineers identified that a very small number of scheduled maintenance items were misaligned between schedules on the aircrafts’ maintenance tracking software and expectations of the timing of those schedules. 

'As a precautionary measure, the Air Corps has temporarily paused PC-12 flying operations while this is addressed.’

Other queries were then referred to the Department of Defence. 

But in response to queries, Minister Helen McEntee’s department would only say: ‘The Defence Forces Press Office have answered this comprehensively and the Department of Defence has no further comment to add.’

The contract for the Pilatus PC-12s was signed in December 2017. 

The list-price for each of the four planes was €4.17million, but the total cost soared to almost €50million for upgrades including specialist equipment and spares.