New Zealand's air force said on Wednesday it had evacuated three people from a United States research base in Antarctica, in what it said was a high-risk operation in freezing temperatures and perpetual darkness.

A flight to Antarctica is among the hardest in the world because of the freezing conditions and because a runway must be physically created on the ice.

A New Zealand air force C-130J Super Hercules crew completed a high-risk midwinter medical evacuation from McMurdo Station in Antarctica, U.S. and New Zealand officials said.