Sydney - A helicopter mission to rescue 52 passengers trapped on an icebound Russian research ship finally got under way in Antarctica on Thursday after a number of false starts and failed icebreaking attempts.
The MV Akademik Shokalskiy has been trapped in thick pack ice 100 nautical miles east of the French base Dumont d'Urville since 24 December, with several icebreakers forced back to open water by impenetrable floes.
A helicopter rescue was announced on Tuesday, but heavy rain and winds saw it shelved until Thursday morning, when a second attempt was foiled by unfavourable sea ice.
The Australian Maritime Safety Authority (Amsa) said a complex, multi-vessel rescue operation would go ahead as soon as weather and ice conditions permitted, with the situation likely to change rapidly.
By late afternoon a favourable window had opened, with expedition leader Chris Turney announcing that a helicopter from the nearby Chinese icebreaker Xue Long had arrived at the marooned ship to begin evacuating passengers.
"The Chinese helicopter has arrived at the Shokalskiy. It's 100 percent we're off! A huge thanks to all," Turney tweeted.
His posting was accompanied by footage showing the Xue Long's red helicopter touching down on a landing pad marked out on the ice beside the Akademik Shokalskiy and an orange-suited rescue crew disembarking.
A second video, posted about an hour later and shot from the deck, showed the first group of passengers trekking across the ice to the helicopter.
Amsa said it was awaiting formal confirmation from the Xue Long that the Antarctic rescue operation had begun.
It is expected to take at least five hours to ferry all passengers from the icebound vessel to the Xue Long - 10 nautical miles distant - by helicopter, with five flights of up to 12 passengers and a return journey taking 45 minutes.
Under the aerial rescue plan outlined by Amsa earlier on Thursday the passengers will be moved from the Xue Long to Australia's Antarctic supply ship the Aurora Australis via a barge.
It will be some weeks before they reach dry land, with the Australis having to travel via Australia's Casey Antarctic base to refuel.
There will be two additional flights to transfer equipment and luggage, and the ship's 22 crew will remain on board until the ice breaks up and the Shokalskiy can sail on under her own steam.
The ship is well provisioned and those on board have not been in any danger.
The helicopter operation follows several failed icebreaking attempts, with the Xue Long, Aurora Australis and French-flagged L'Astrolabe all forced to turn back by thick ice that they could not break through.
Passengers on the stranded ship - an eclectic mix of scientists, tourists and journalists - had been following in the footsteps of Australian Sir Douglas Mawson and his 1911-1914 expedition.
The team has been carrying out the same scientific experiments that Mawson's group conducted during their expedition, partly in an attempt to discover how quickly the Antarctic's sea ice is disappearing.
Board games, first-aid and other skills courses and walks on the ice have helped to pass the time. They even penned a theme song about their adventure and filmed themselves singing it on the top deck.
Though they are in remote Antarctica the group dropped in on one of the world's biggest New Year's parties, broadcasting live to celebrations in New York's Times Square from their marooned vessel.