(CNN) -- Slowed, but not daunted, by Antarctic winds topping 100 mph, low visibility and snow, rescuers Saturday pounced on improving weather conditions to move closer to where a plane carrying three Canadians sent out emergency beacon signals.
The condition of the three crew members on the Twin Otter operated by Calgary-based Kenn Borek Air Ltd. was not known nearly three days after the flight went missing and rescue attempts began.
The plane was flying from the South Pole to an Italian base at Terra Nova Bay, Maritime New Zealand said.
"It is difficult to think of a more difficult environment," said Steve Rendle, spokesman for Rescue Coordination Centre New Zealand.
The beacon stopped working Thursday evening, possibly because the battery had run out, about a day after the plane was reported missing. By then, rescuers had pinpointed the location, but harsh weather has made visual sightings impossible, Rendle said. Winds, for example, reached nearly 105 mph Wednesday.
One search aircraft reached a camp about 30 miles from where the beacon sounded. Two helicopters were moving toward the forward base on a glacier Saturday afternoon. A C-130 Hercules aircraft circled the beacon activation site, attempting to make visual contact.
"We've got a reasonably positive forecast for that site," Rendle said from Wellington.
The missing crew's survival kit includes survival suits, mountain tents and enough food and water for five days.
The aircraft is believed to be at a height of 13,000 feet near the top of Mount Elizabeth, part of the rugged Queen Alexandra Range. It is a long distance from any bases in Antarctica.
"We would expect them to be with the plane," Rendle said of the crew. "Common sense would dictate you stay with the beacon."
Kenn Borek Air Ltd. did not immediately return a message left by CNN on Friday night.
In a statement Wednesday, the airline described the flight as overdue. It did not release names of the crew members.
According to its website, the airline has one of the largest Twin Otter fleets in the world.
"We are best known for our remote polar services utilizing ski-equipped Twin Otter," it said. "KBAL provides a wide range of additional services including medevac, survey, paradrop, float operations, third-party maintenance and overhaul."
The Queen Alexandra Range, about 100 miles long, was named by Ernest Shackleton during the British Antarctic expedition in 1907-1909.
Peter West, spokesman for the National Science Foundation, which oversees the U.S. Antarctic Program, said 24 hours of daylight this time of year should help rescue efforts.
CNN's Dave Alsup and Erica Harrington contributed to this report.