A small plane took off from a British Antarctic base tonight to rescue a sick American doctor at the South Pole.
The daring rescue was launched hours after a New Zealand air force plane retrieved four sick Americans from a frigid research station on the other side of Antarctica.
‘‘They’re off,’’ said Valerie Carroll, a spokeswoman for Raytheon Polar Services, after the eight-seat Twin Otter plane left Rothera base on the Antarctic peninsula.
The departure came after a two day delay forced by blowing snow and low visibility, postponing efforts to reach Dr Ronald Shemenski at the Amundsen Scott-South Pole station.
Carroll said clear skies and improved conditions at the pole allowed the departure.
She said the plane, making an expected 10 hour flight, would reach a point of ‘‘safe return’’ at 2130 BST.
At that point, she said, the pilots were to decide if conditions would allow them to continue on to the South Pole, where they would refuel for the flight back with Shemenski.
Shemenski, the only physician among 50 researchers working at the Amundsen Scott-South Pole station, recently suffered a gall bladder attack and has been diagnosed with the potentially life-threatening condition known as pancreatitis.
The plane en route to the pole is fitted with skis for landing gear. It arrived with a back-up aircraft late last week in Punta Arenas, Chile, the last stop in the Americas en route to the South Pole to pick up the 59-year-old doctor.
Flights to the South Pole station are normally halted from late February until November because of the extreme winter cold and darkness. But the rescuers worried that Shemenski’s condition would worsen in the coming months, when an airlift out of the South Pole would be virtually impossible.
A New Zealand air force plane returned safely today after retrieving four ailing Americans from an Antarctic research.
Their hand forced by the health emergency, the rescuers and their Hercules plane braved a landing and take-off on McMurdo Antarctic Base’s ice runway on the last day of sunshine before the black polar winter.
The plane returned safely to Christchurch, New Zealand late in the day, 15 hours after it had begun its round-trip journey.
Two of the evacuees were suffering from ‘‘critical conditions,’’ government research group Antarctica New Zealand said in a statement. The two had been transferred to a hospital in Christchurch, where their conditions were stable Tuesday night, the statement said. It gave no further details.
Officials involved in the first rescue said the mission got a lucky break, leaving an hour earlier than scheduled and avoiding deteriorating weather conditions in Antarctica.
‘‘It was very fortunate that we got in there on time, and out,’’ said mission commander John Cummings said.
At McMurdo, the plane spent just one hour on the ground to pick up the evacuees and refuel. Its engines were kept running throughout the stopover to prevent them freezing in the air, which was 22 degrees below zero Fahrenheit.
‘‘The weather was a little bit iffy but we managed a quick change down on the ice,’’ pilot Nathan McDonald. ‘‘It was a very successful day.’’
There are 211 Americans left at the base following the evacuation, where they will winter until the next flights, scheduled in late August as Antarctica’s spring begins. The evacuation flight carried fresh fruit and vegetables and personal mail to the ice-and-snow-bound base staff.
Antarctica is home to nearly 90% of the world’s ice and 70% of the globe’s fresh water. The third-largest continent, it is one and a half the size of the United States.
Nations including the United States, Britain, Australia, New Zealand, France and Argentina carry out experiments at bases dotted across the continent. They are regularly serviced by flights during the summer months but batten down the hatches and reduce staffing for the polar winter.