MANILA - The Philippine Air Force (PAF) on Friday said four of its personnel were killed when a helicopter on a training flight crashed shortly after takeoff in Cauayan City, Isabela Thursday night.

In a statement, PAF expressed mourning for the air officers who perished, the identities of whom are still being verified.

Those who died included two pilots, one other officer, and one of two aircrew from PAF's Tactical Operations Group 2. The other aircrew who survived is undergoing treatment for injuries.

"The PAF, and the AFP (Armed Forces of the Philippines) as a whole, shares the grief and extends its sympathy to the bereaved families and colleagues of the airmen who perished in this air operations mishap," it said.

AFP spokesperson Maj. Gen. Edgard Arevalo said the chopper, with a total 5 on board, were "conducting proficiency training for night flying when the accident happened."

The Air Force said an investigation team has been sent to the site of the crash to determine the cause of the accident.

Deadly air crashes periodically occur in the Philippine military, which continues to struggle to upgrade its modest and aging air fleet.

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