Poor weather is hampering the New Zealand-led search for three Canadian men, reported missing on a flight from the South Pole to Terra Nova Bay.
The Rescue Coordination Centre New Zealand, US officials at McMurdo and Italian authorities are involved in the rescue mission.
A search was launched after the men's Twin Otter aircraft's emergency locator transmitter was activated about 10pm yesterday.
The beacon was transmitting from the northern end of the Queen Alexandra Range, within New Zealand's Search and Rescue Region - about 670km from Scott Base and 450km north of the South Pole.
Search and Rescue Mission Coordinator John Ashby said a DC3 aircraft was over the site of the beacon, but heavy cloud was preventing visual contact.
Fixed wing aircraft and a number of helicopters, including a Southern Lakes (New Zealand) helicopter on contract to Antarctica New Zealand at Scott Base, were on standby waiting for weather conditions to allow them to travel to the area.
"Weather conditions are extremely challenging,'' John Ashby said.
"There are winds of 90 knots at the site, and conditions are forecast to worsen with snow becoming heavier.''
However, when weather conditions allowed, a joint New Zealand and US field rescue team was ready to go,'' Mr Ashby said.
"We have been advised that the plane is equipped with survival equipment, including mountain tents, and supplies sufficient for five days.''
The missing aircraft was owned and operated by Kenn Borek Air Ltd, a Canadian firm headquartered in Calgary that charters aircraft to the US programme.