What happened to a pilot and four passengers aboard an ill-fated flight that went missing between Christchurch and Milford Sound 60 years ago is still a mystery.

On 12 February 1962, pilot Brian Chadwick and the group took off on a scenic flight in his Dragonfly aircraft, never to be seen again.

The four passengers - Louis Rowan, Darrell Shiels and newly-wed couple Elwyn and Valerie Saville - were all Australian.

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.

He said people are still searching the West Coast for the plane wreckage.

"I still receive at least monthly e-mails and phone calls from a range of people who have either found items, have theories of where the aircraft wreckage is located, or have undertaken their own private searches in 'hot spot' areas," he said.

"For example, before Christmas an aircraft seatbelt buckle was found on a South Westland beach and has been investigated by the police."

Waugh said Covid-19 had scuppered plans to commemorate the anniversary - which included an airworthy Dragonfly ZK-AYR flying to join a gathering hosted by the Canterbury Aero Club, joined by relatives from Australia and New Zealand.

Filmmaker Bobby Reeve and his family have been looking for the Dragonfly since 2008 - most summers they tramp up the Huxley River deep into the Brodrick Pass on the South Island's Main Divide.

Reeve told RNZ last year that after speaking to witnesses and friends of the pilot, Brian Chadwick, he believed the wreckage was in that area.

"He would have known roughly whereabouts he was and probably entered the cloud thinking he was high enough to get through the pass and he's been off to one side or the other.

"When you look at the area up there, it's an area where nobody would go, no-one would just stumble across it."

This women's fashion shoe was found hours from the nearest town. Photo: SUPPLIED

Reeve said the discovery of a woman's boot in the remote location has led them to believe the plane was about 8000 feet up, deep in the permanent snow.

"I think if it had been in the bush the whole time it would be covered in moss - but it wasn't which is why I think it's come down off the snow."

Republished by Arrangement