A Calgary-based team's perilous mission to fly in and rescue up to two people in need of medical attention from a research facility in the Antarctic is now underway.

The crew arrived on Tuesday afternoon and the U.S. National Science Foundation said they will rest for 10 hours before making the return journey.

The small Twin Otter plane operated by Calgary's Kenn Borek Air made the 2,400 kilometre, nine-hour trip on Tuesday through the dark and cold from a British base on the Antarctic peninsula.

Two of the 48 people at the South Pole station are ill and at least one of them needs medical care off the continent.

Officials are still determining whether the second patient needs to be brought out as well, but have not given any details on the person or condition.

It's mid-winter in Antarctica and the foundation said flights in and out of the station are usually not planned between February and October due to the extreme cold and darkness.

The foundation said the aircraft that Kenn Borek Air flies are able to operate in extremely low temperatures and can land on skis. Because there is no tarmac runway at the South Pole, it said the aircraft must land in total darkness on compacted snow.

Kenn Borek provides contractual logistical support to the Antarctic Program, according to the foundation, and conducted similar evacuations in 2001 and 2003.

At Rothera, the aircrews prepared the aircraft, including equipping them with skis for a landing on snow and ice at the Pole.

One plane flew to the Pole for the medical mission, while the other remains at Rothera to provide search-and-rescue capability if needed.