Slow withdrawal from Antarctica

New Zealanders and Americans are due to start returning from Antarctica this week but soft snow on the ice runway means more flights on smaller, ski-equipped aircraft will be used.

About 1100 researchers and support staff and 43 tonnes of cargo must be flown from New Zealand's Scott Base and the nearby US McMurdo Station to Christchurch as the Antarctic summer season ends.

The United States Air Force usually sends C-17 Globemaster aircraft, which can carry more than 120 people, to do the task.

"This year, however, the snow and ice runway the big jets, and other non-ski aircraft, use to land on is too soft to support their weight," the USAF said in a statement.

Instead, seven ski-equipped LC-130 turboprop aircraft will be used. They can only carry up to 40 people on each flight and take longer to make the 3800km journey.

Last year, volcanic dust and dirt blanketed the airfield. The dirty snow and ice melted rapidly, causing similar problems for the C-17.

Colonel Shawn Clouthier, the commander of New York National Guard's 10th Airlift Wing, said 284 missions would be flown this summer, a 57 per cent increase in workload.