The U.S. National Science Foundation said the medical evacuation was due to end a little after 2 a.m. EDT (0700 GMT) on Thursday when a A319 Airbus from Australia's Antarctic research program was due to land with the American patient in Christchurch, New Zealand.

The Airbus had already completed the most perilous part of its journey when it touched down on an ice runway or landing strip known as Pegasus near McMurdo Station, one of three year-round research outposts the National Science Foundation runs in Antarctica.

Flights to Antarctica are usually only made in the summer, but the NSF said the patient - an American member of one of its projects - "may require immediate corrective surgery."

Antarctica is currently emerging from its six-month-long night. There is now a period of twilight at midday that may have assisted pilots in landing on the ice runway.

(Reporting By Tom Brown; Editing by David Brunnstrom)

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