NZ's 'Bermuda Triangle' mystery: Where is missing pilot?

Ryan Moynihan was flying a Cessna from Canterbury to Haast when he disappeared in 1997. Photo / TVNZ

A final hunt is planned in one of New Zealand's most puzzling aviation mysteries - the disappearance of a young pilot and his aircraft almost 15 years ago.

Ryan Moynihan, then 23, was flying from West Melton, in Canterbury, to Haast in his Cessna in November 1997 when he vanished on his way to an area known as New Zealand's Bermuda Triangle.

Despite extensive searches, including one in 2007 involving almost 100 volunteers, no trace has been found of pilot or aircraft.

Ryan's father, Michael Moynihan, wants him to be found but isn't getting his hopes up after years of false leads.

Westpac rescue pilot Darryl Sherwin plotted radar co-ordinates that helped find multimillionaire Michael Erceg's crashed helicopter near Raglan in 2005, and is using a similar technique in the Moynihan mystery.

Last November he hired two aircraft similar to the missing plane and, with the Rescue Co-ordination Centre and Airways New Zealand, tried to replicate Mr Moynihan's flight path in the Mt Peel area - where Mr Sherwin originally thought he crashed.

But that trial showed Mr Moynihan could have flown over the mountain ridge.

"What we discovered is that we weren't picked up on primary radar at all. Which means the information I was using initially - that he faded off radar because he was below 3000ft [914m] - may be wrong."

But he is still not convinced, and wants to have "one last look" in a rugged gully on the side of Mt Peel later this year.

Several aircraft have gone down in rugged South Island terrain between Milford Sound, Mt Aspiring and Haast and never been found.

Mr Sherwin didn't know the Moynihan family before the crash, but says the mystery has "bugged me for a long time".

Michael Moynihan told the Herald he believed his son did reach Haast and struck a storm.

"There's a theory he put it down on a beach and refuelled and the front went past and he thought, 'I better get going', and there was another front coming and he got caught between the two of them."

He said the family didn't know any more than they did 15 years ago, "but there's still people looking - it's amazing".

"I hope something does come up one day just to finalise it."

He said the mystery was beyond frustrating for him and his wife, Robyn.

"I just want to know what happened, but my wife is more realistic, She knows he is not coming back so why keep hunting for him?"