Three new fixed wing aircraft are being bought for the Air Corps at a cost of €32m.
The Pilatus planes will replace the five Cessna aircraft bought in 1972.
They will be equipped for surveillance, intelligence gathering and logistical support.
The Department of Defence say the aircraft can operate 24/7 and in all weather conditions.
Exciting day for @IrishAirCorps delighted to sign €32m contract for three new fixed wing utility aircraft. Government will continue investment in @defenceforces in 2018. pic.twitter.com/zPY5ruqVhT
— Paul Kehoe T.D (@campaign4kehoe) December 19, 2017