A child recovery specialist will land in New Zealand on Monday to aide the search for missing yachtie Alan Langdon and his 6-year-old daughter Que.
Experienced seaman Langdon, 49, and his daughter left Waikato's Kawhia Harbour bound for the Bay of Islands on December 17 and have not been seen or heard from since.
Border alerts are in place and Interpol is working with New Zealand police, while Langdon's bank accounts and phone records are also being checked as the search for the missing pair ramps up.
Australian child recovery specialist Col Chapman thought Langdon is likely to be sailing his tiny catamaran to Australia, where Chapman believes he has disappeared with Que previously. When Chapman arrives he wants to pore over the available information and try to eliminate conflicting reports. He will then discuss with Que's mother Ariane Wyler whether they should fund any additional elements of the search like an extra plane.
"There's a lot of nooks and crannies in New Zealand. Lots of little places he could easily be and more so if he's trying to hide.
"He could easily just be pulled up on a bank somewhere.
"Everyday we're expecting them to stick their heads up and Alan to say 'oh you've all overreacted'."
Chapman said there was a "99 per cent chance" Langdon was not in New Zealand and had made a dash for Australia. He estimated the crossing of the Tasman Sea in Langdon's vessel, which travels at about six knots, would take between 30 and 45 days.
"He's announced to many people, friends, family, that this boat will make it to Australia and back 10 times, no problem," Chapman said.
"Some people say the boat was heavily stocked to the gunnels with no room left ... and stores for over 30 days.
"It would be a challenging trip, and one I wouldn't do, and one many people wouldn't do. But someone with Alan's skills, could easily do it."
Langdon's 6-metre white wooden Tiki catamaran, which has blue anti-fouling paint under the waterline, is modified with a Bermuda mast, and sail ID number of T878, has a capacity to carry about 500kg in stores, Chapman said.
Calculating tides and winds, and depending on Langdon's tacking, the boat would currently be between 400 to 700 nautical miles off the New Zealand coast, he said.
"It's a big trip but once he crosses a line a couple of hundred kilometres offshore [of Australia], he looks like a coastal cruiser. He doesn't look like he's come from New Zealand in that little thing."
Chapman thought Langdon would avoid other countries because the pair would stick out too much. But the pair could easily hide in Australia. The father and daughter were previously tracked to a New South Wales town of Nimbin where they were living in a campervan on a large farm.
"Anyone who wants to hide is there. No one asks questions."
Chapman said he gets around 30 phone calls a week from parents searching for their children. They find over 70 per cent of the children, and of that they recover 95 per cent.
"I see the strongest of parents break down. They're a mess. There nothing worse especially when the child is presumed abducted but unknown.
The official search is now concentrated in the Northland area after police received sightings of a vessel similar to Langdon's heading in that direction over the past few days.
The girl's mother, Ariane Wyler, told the Herald that she separated from Langdon last year.
Wyler - who lives at Golden Bay in the South Island but is on holiday in her native Switzerland - hired Chapman to help find her daughter who she has not seen for 20 months.
"I am deeply distressed about this current situation and miss my daughter Que greatly," she said.
"I am strongly convinced that they both are alive, well and safe. I believe in Alan Langdon and his capabilities as a seagoing person. My gut feeling tells me that they are further offshore to the west."
She described Que as a "beautiful daughter" and a "gorgeous little person".
Chapman said it's not the first time that Langdon has gone on the run.
In March last year the Langdon family of three - Langdon, Que and Wyler - was in Port Vila, Vanuatu, when Cyclone Pam struck.
The category 5 severe tropical storm battered the island, claiming up to 16 lives and sinking at least 20 boats.
It sank their 46-foot catamaran Sanyasin and the Langdons were lucky to escape with their lives.
After the cyclone, when the Australian and New Zealand air forces were repatriating people, Langdon took off for Australia with Que, Chapman said.
Chapman was enlisted by Wyler to find Langdon who kept moving about.
It's understood that Langdon and Que moved to Kawhia in August where they lived with local woman, Mary Smith.
She said the Langdon family had used her home as a base for years in between travels.
Langdon, a stay-at-home dad, built the catamaran the pair left Kawhia in on Smith's front lawn.
Smith raised the alarm on Boxing Day after Langdon and Que had been at sea without word for nine days.
She described Langdon as a competent boatsman who doted on his daughter.
"She was his best mate. He loved her to the max," Smith said.
Police this afternoon said that an RNZAF P3 Orion has searched the western coastline from Kawhia to Cape Reinga and the eastern coastline to the Bay of Islands, out to 35 nautical miles.
A Philips Trust Air Rescue aeroplane has searched from Mokau to Port Waikato, including harbours and coastline, out to six nautical miles.
Coastguard air patrol have searched, and continue to search, the bays and harbours on both coasts of Northland. Coastguard units have also searched Hokianga and Houhora Harbours.
Maritime NZ continues to broadcast police interest in the vessel on marine channels.
"Police are looking at a multitude of possible scenarios as part of this search, and this includes advising and liaising with Interpol, in the event that Mr Langdon has left New Zealand," a police statement said.
"If you believe you have seen Mr Langdon's vessel in the last few days, or you think you may have information which would assist the search effort, please contact your local police station."