Bomb disposal experts were today making a plane wreckage site safe before investigators could move on to the scene.
An experienced Irish Air Corps instructor and a cadet pilot were killed in the crash in a remote section of mountain valley near the village of Maam Cross in Co Galway.
The pair had been on a low-flying training exercise which left Casement Aerodrome in Baldonnel, Co Dublin, at about 5.45pm last night.
Their two-seater Pilatus PC-9 training plane was fitted with ejector seats which are triggered by explosives, which have to be cleared before the Air Accident Investigation Unit (AAIU) can begin their probe into what caused the crash.
The two men were on one of three Air Corps training flights that left Baldonnel yesterday on a mission to Galway Airport and back.
A woman who raised the alarm reported seeing the stricken plane flying low near the village of Cornamona, Co Galway, just before hearing a loud bang.
"Part of the purpose was to fly low," said a Defence Forces spokesman.
"Low level flying would be 1500 feet so it's not hedge-hopping or nap-of-the-earth flying."
The fatal flight was reported missing at about 6.20pm and an Irish Coast Guard helicopter scrambled from Shannon located the wreckage less than an hour later.
The remains of the two Air Corps members remained at the crash site overnight as investigation and bomb disposal teams made preparations to get to the scene.
The Defence Forces spokesman said weather conditions were good at the time of the take-off from Baldonnel but inquiries would look at the conditions in the west of Ireland at the time of the crash.
The Air Corps have eight Pilatus PC-9M aircraft.
The two seater turbo propeller planes are used mainly for training pilots and instructors and as close air support craft.
President Mary McAleese said she was shocked and saddened by the tragic deaths.
"The sympathies and prayers of the nation are especially with the families and colleagues of these two young men who lost their lives so suddenly," she said.
"This is a devastating loss for the Air Corps and the Defence Forces."Reuse content