The bright yellow plane is based in Auckland while it's believed the owner got his father to carry out the test flight for him. The owner's father, who died, lives in the Marlborough region.
It is not known who was flying the plane when it crashed.
According to CAA information, the victim's son has owned the plane since June last year and been flying for about two years.
A police spokeswoman said it's believed the plane had taken off from the Tasman area in the South Island and was headed to Auckland.
The plane the pair were flying in was a Vans-RV4, one of the most popular light aircraft in America, Australia and other parts of the world, an industry insider says.
He had seen the plane in Waharoa before but had not seen it for a few months.
On Monday residents and witnesses recalled seeing the plane performing a "strange manoeuvre" before careering to the ground.
A group of trainee pilots saw the plane performing an aerial manoeuvre before they lost sight of it.
They thought it the plane was flying "pretty low for what it was doing".
They said they didn't see it crash and weren't sure what had happened but believed it had somehow lost control.
The group said they were trainee pilots and the crash had freaked them out "a bit".
Another neighbour said he heard what he thought first was a car crash, before his neighbour alerted him to the downed plane.
Together the man and woman raced over to the crash to see if they could help but the two occupants had already died.
"Police offer their sympathies to their friends and family at this sad time," a spokesperson said.
Police are working with the Civil Aviation Authority to identify the cause of the crash.
As part of those inquiries police would like to hear from anyone who may have seen this small yellow aircraft approaching Raglan on the afternoon of the crash.
Anyone with information is asked to contact Detective Sergeant Rene Rakete from Huntly Police on (07) 828 7560.
