Flying in Antarctica - where's the runway?

When US scientists last visited this Antarctic peak in 1975, they used dogsleds in a gruelling trip over crevasses. Now, pilot Steve King swoops down and coolly lands his plane on a snowy ridge at the top.

For me - sitting beside Mr King in the co-pilot's seat of the red Twin Otter plane - the landing on the trackless, bumpy white surface in the Antarctic Peninsula is unforgettably terrifying.

"This is easy," shrugs Mr King, a 52-year-old Canadian with 18 years experience of polar flying. "It's landing at the North Pole that's hard with sea ice." In one day, he made four landings on snow and ice.

Planes have transformed science in Antarctica by making some of the least accessible spots on the planet easier to get to - at least when the weather is clear. For first-time passengers it's nail-biting.

At Merger, a "nunatak" or rocky peak sticking out of the ice, the only evidence of a visit by US scientists in 1975 is a tiny metal stake covered by a pile of rocks. They also oddly left a tin of butter - whitish goo is visible through the rust.

Mr King landed the red Twin Otter plane, which has skis alongside wheels - on the slushy snow to within metres of where British scientist Alison Cook wanted to get satellite readings to update the maps compiled in 1975.

"We've got it easy," Prof. Cook, who works for the British Antarctic Survey, said on the barren peak in bright sunshine overlooking the Wilkins Ice Shelf. Our visit lasted about two hours.

She brought notes by a scientist on the 1975 expedition by the US Geological Survey warning of "heavy crevassing, difficult crossing from Alexandra Island" and details about where to camp for the night.

"They had to drag their sledges with dogs," she said. Dogs have been banned from Antarctica since 1994 as part of a treaty to limit environmental damage to the frozen continent.

Earlier in the day, Mr King landed on a mountainside on the Beethoven Peninsula to the south - he had to park the plane at an angle on the snow to ensure it did not slide downhill towards crevasses in the distance. After Prof. Cook took measurements, Mr King accelerated down the slope and took off - the five of us passengers broke out into relieved applause.

With some of the strongest winds on earth, Antarctica is among the most perilous places to fly. In the worst disaster, a New Zealand tourist flight crashed on Mount Erebus in 1979, killing all 257 people aboard.

Before landing, Mr King flies his plane around several times searching for a suitable spot. He abandoned one planned landing by another nunatak as too risky.

After spotting a suitable spot, he flies in low and drags the skis over the snow to get a feeling for the surface. "If you touch down near a crevasse the weight is still on the wings," he said. After this kind of check he decides whether to land.

But fliers need good visibility - storms and high winds often make visits impossible. Some scientists have come all the way to the nearby Rothera research station but had to abandon visits - often years in planning - to remote spots.

One other worrying moment was when a loud buzzer went off in King's plane - meaning it had slowed to stalling speed of about 104.6 kilometres per hour and was falling out of the sky. Less than a second later, the skis touched the ground.

"I want to be flying as slow as I can to land," Mr King said.