Nearly 54 years after a plane went missing between Christchurch and Milford Sound, two groups are still searching for it on either side of the South Island.
It was 12 February 1962 when pilot Brian Chadwick took off on a scenic flight in his Dragonfly, never to be seen again.
He had four passengers on the flight: Louis Rowan, Darrell Shiels and newly-wed couple Elwyn and Valerie Saville, all from Australia.
Despite one of the most extensive aerial searches in New Zealand history, the plane was never found.
Richard Waugh, whose father was good friends with the pilot, documented the flight and the mystery surrounding it in a book, Lost Without Trace: Brian Chadwick & the Missing Dragonfly.
It was one of the biggest aviation mysteries in New Zealand, he said.
"I remember as a young boy, my father talking about it, he spent years looking for his friend and the plane."
It is Mr Waugh's book that has sparked people's interest and led them into the bush in a bid to find the plane.
Filmmaker Bobby Reeve and his family have been looking for the Dragonfly for eight years, filming their efforts as they go.
On the day the plane went missing, there were 18 reported sightings in both the east and west - but Mr Reeve said all the evidence pointed to the plane being in the Hopkins Valley, in the east.
"We've been around the country and interviewed people who reported sightings of the plane that day, and from that we are certain it is in the Lake Ohau, Hopkins Valley, area.
"It's a long way up there - it's probably a good 50km off the road, as far as we can take our bus - then we drive another 10km by Land Rover, crossing three rivers at the same time before we can even start walking into the valley," Mr Reeve said.
Mr Reeve, his wife and two sons spend up to six weeks at a time living in the remote valley, grid-searching the dense bush for the Dragonfly.
A find last year further convinced Mr Reeve he was looking in the right spot.
"We found a ladies' fashion heeled boot. As soon we saw it, we knew it was out of place - a four and a half [hour] walk from civilisation in a mountain stream, so we know we are getting close to the Dragonfly."
At 73, he said he realised he would not be able to search forever - but he would continue to do so as long as his health let him.
"Sometimes we come out and think 'it's so dangerous, we won't go back in'. My son Simon fell down a 30ft cliff; his pack broke his fall. We've been very lucky."
Second search team
Another group searching for the plane are convinced it is on the West Coast.
About eight people, led by Gavin Grimmer, head up the Jacobs River near Fox Glacier for a few days every February looking for the plane.
"After 18 months of full-time research, I discovered there was heaps of evidence to say it was on the West Coast, and nothing that proved reliable on the East Coast, Mr Grimmer said.
Alec Doig, who has been part of Mr Grimmer's team, said the area was extremely harsh bush.
"We get dropped in by helicopter, otherwise it would take half a day to walk there - it's thick, dense bush up the valley... There are boulders the size of houses in there that we have to find our way around."
Once in, he said, the group would set up camp then spread out to search - looking for anything out of place.
"We are constantly looking for anything that resembles a plane, or something manmade."
Mr Waugh said people like Mr Reeve, Mr Grimmer and Mr Doig kept the legacy of the Dragonfly alive.
"If the plane was ever found, I would be so excited to tell the families of those on board.
"Being a chaplain in the aviation industry, I would visit the site and say some prayers. After all, it is the final resting place of five people."
He said he expected deteriorating weather had caused carburetor icing - but, until the plane was found, nobody would ever know what happened that day.
As the official air accident report put it: "The aircraft disappeared in the course of a flight from Christchurch to Milford Sound but the reason for its failure to arrive at its destination has not been determined."