Search and rescue workers from New Zealand are hoping to make visual contact with three Canadians whose aircraft disappeared days ago on the continent, and are believed to be stranded.

Rescuers issued an update Saturday afternoon, local time, saying they had arrived at a temporary base 50 kilometres from the location of the missing Twin Otter plane.

Fierce winds, snow and low cloud cover have hampered search efforts since the plane, operated by Calgary-based Kenn Borek Air, went down near the northern end of the Queen Alexandra mountain range, some 450 kilometres from the South Pole.

New Zealand Rescue Co-ordination Centre is organizing the search with the help of Canadian and U.S. authorities.

The missing plane had been transmitting an emergency beacon signal since late Wednesday, local time, alerting rescuers to the plane's exact co-ordinates, but the battery appears to have since died.

Rescuers have pinpointed the plane to be halfway between the South Pole and McMurdo Station, a U.S. research facility in Antarctica.

A rescue official said Saturday that two helicopters from Scott Base, a research facility on the continent, were to arrive at the temporary base at 4 p.m. local time to assist with the search.

Cloud cover was still an issue in getting a visual on the plane, a rescue official told CBC News.

A plane circled over the site of the signal Friday morning, local time, but clouds and wind prevented visual contact and the search was put on hold.

"Today was a frustrating day for all concerned," said Conrad Reynecke, a spokesperson for the rescue centre.

It is not known if the missing plane crashed or made a forced landing. The conditions of the pilot — Bob Heath from Inuvik, N.W.T. —  and his two unidentified crew members, believed to be the co-pilot and flight engineer, are also not known.

"It is very difficult to speculate as to what we will find when we get there," said Reynecke.

"We’ve been told that this gentleman is a very experienced pilot and he could probably land it in the most inhospitable cases. So the best-case scenario is we find a tent set up and people waiting for rescue," he said.

"But, worst-case scenario, we do not want to think about it. This remains a rescue operation."

Experienced Antarctic pilot

 But even in favourable weather, flying at that altitude, roughly 4,000 metres, poses "significant challenges," said Reynecke.

Mark Cary, a former pilot with Kenn Borek Air, said he flew with Heath on a number of occasions and described him as an experienced aviator who was well versed in cold-weather survival techniques.

"I’m very, very confident that if this crew indeed survived getting the aircraft on the ground that Bob is the kind of individual that would be able to survive until rescuers could get to him and his location," he said.


The Canadian pilot of the missing Twin Otter was identified by his wife as Bob Heath of Inuvik, N.W.T. (Courtesy Lucy Heath)

Jim Pearce, a retired pilot with the company who flew with Heath, described him as  "probably one of the most experienced Antarctic pilots in the world today. It's a very very challenging place to work, and a very, very challenging place to fly."

He said the airline would have provided Heath and his passengers with the best survival gear available. "They'd have extreme cold weather gear available, and the most up-to-date survival packs," he said.

An undated video, posted earlier this week to YouTube, features Heath giving safety instructions to his passengers.

The missing plane had been flying from the South Pole to an Italian base in Antarctica's Terra Nova Bay. A spokesman for the U.S. National Science Foundation has said the flight was in support of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development.

With files from The Canadian Press