New questions about the movements of John Beckenridge in the weeks before he snatched his stepson from school and disappeared have been raised after investigations by NZME News Service.
Authorities in Papua New Guinea, where Mr Beckenridge worked for several years as a helicopter pilot, say a man entered the country on a cruise ship in February using one of Mr Beckenridge's known aliases - that of 61-year-old Australian passport holder John Locke.
An official with the Immigration and Citizenship Service Authority said a Mr Locke arrived at the port of Alotau in Milne Bay Province on a ship from Brisbane on February 17.
He had been due to leave Papua New Guinea by April 19 but there was no record of him having done so. He is viewed as an overstayer and authorities will investigate further.
Mr Beckenridge, a 64-year-old born in Sweden, worked for an aviation firm based in Goroka, capital of the Eastern Highlands province in Papua New Guinea before he quit last September.
He abducted stepson Mike Zhao-Beckenridge, 11, from James Hargest College's junior school in Invercargill on March 13 after losing a custody battle.
His car was recovered from the sea beneath cliffs at Curio Bay in Southland in May. Police have been unable to confirm whether the pair were in the car when it hit the water. Their bodies have not been found.
Some friends and neighbours of Mr Beckenridge believe he faked the deaths and fled New Zealand, possibly to Papua New Guinea.
Police are treating the disappearance as a missing persons case rather than a murder-suicide. They have border alerts and are working with Interpol
Mr Beckenridge, who has lived in Australia and once worked as a pilot in Afghanistan before one of his colleagues was shot down and killed, has several known aliases. As well as John Locke, they include John Robert Lundh, Knut Goran Roland Lundh and John Bradford.
The Immigration and Citizenship Service Authority official said they had not been approached by police from New Zealand or Papua New Guinea, or Interpol about the Beckenridge case.
However, Southland area commander Inspector Joel Lamb said police know the movements of Mr Beckenridge and his known aliases until the time his dark-blue Volkswagen Touareg went into the sea.
"Our staff have continued to work with the Wellington Interpol Office since Mike and John went missing," Mr Lamb said.
"This work includes the liaison with overseas agencies, however, the details of the specific agencies and interactions remain part of the investigation and police are unable to comment further.
"Border alerts also remain in place for all known passports held by Mike and John, and to date, these have not been triggered. This, accompanied with the information currently available, suggests that Mike and John have not left the Catlins area."
Mike Zhao-Beckenridge's mother declined to comment.
Mr Beckenridge, who was living in an upmarket Queenstown estate before disappearing, was well-known in Papua New Guinea flying circles.
Pilots recall an experienced, talented and popular commercial pilot.
Pacific Helicopters PNG chief executive Mal Smith, who has been interviewed by police, said he knew Mr Beckenridge had been having "problems getting access to his kid but we didn't know it was to that extreme". He was unaware of Mr Beckenridge's multiple identities.
Aviation expert Peter Clark has said it would be "improbable but not impossible" to flee New Zealand by helicopter.
It would likely require a "fairly capable machine", extra fuel tanks, and a stopover, likely at Norfolk Island.
Criminologist Greg Newbold has said other people have escaped New Zealand undetected.
He believed it was possible for someone as resourceful and clever as Mr Beckenridge to do so. The most likely method of leaving the country was by boat, he believed.
Police have been receiving tipoffs from the public that suggest the pair might be hiding out in New Zealand. However, every sighting has been ruled out after checks.
Customs, which controls New Zealand's borders, has previously refused to comment on the Mr Beckenridge case, referring inquiries to police.
The search for Mike
John Beckenridge, 64, takes stepson Mike Zhao-Beckenridge, 11, from Invercargill school, in breach of parenting order
Police seek help to find the pair, thought to be travelling in a dark-blue Volkswagen Touareg
March 21 and 22
Confirmed sighting of the pair in bush in the Slope Pt area in the Catlins; items of interest found in Curio Bay area
Police divers join search at Blue Cod Bay, but conditions too rough
Police find vehicle wreckage in Blue Cod Bay; "grave fears" for Mike
Wreckage confirmed as Volkswagen Touareg
Police divers confirm car is Beckenridge's
Detective says "all the evidence" points to the pair being inside the car when it plunged off a cliff
Divers and helicopter recover car, which is taken by boat to Bluff
Police forensic examinations find "no signs of human remains" in car