Passengers from the Russian ship MV Akademik Shokalskiy trapped in the ice 1,500 nautical miles south of Hobart, Australia, walk around the ice. Pic: AP.

CANBERRA, Australia (AP) — The latest attempt to rescue passengers on board a research ship that has been trapped in Antarctic ice for more than a week was delayed again Thursday after sea ice prevented a barge from reaching one of the rescue vessels.

The Australian Maritime Safety Authority’s Rescue Coordination Centre, which is handling the operation, said earlier on Thursday that weather conditions had improved and rescue flights were expected to commence. A helicopter was expected to airlift passengers to a Chinese icebreaker, the Snow Dragon, and a barge would then ferry them to a nearby Australian vessel.

But before the rescue operation could begin, sea ice had blocked the path of the barge that needed to make it from the Australian vessel, the Aurora Australis, to the Snow Dragon. Because the Aurora isn’t built to handle a helicopter landing, it appeared unlikely that the passengers would be rescued Thursday, the maritime authority said.

“This rescue is a complex operation involving a number of steps. Operations in Antarctica are all weather and ice dependent and conditions can change rapidly,” the agency said in a statement.

The rescue operation for the 74 scientists, tourists and crew on the Russian ship MV Akademik Shokalskiy has been plagued by one delay after another since the vessel became stuck on Christmas Eve. Three icebreakers were initially dispatched to try and crack their way through the thick ice surrounding the ship, but all failed. The Aurora came within 20 kilometers (12 miles) of the ship Monday, but fierce winds and snow forced it to retreat to open water.

Officials had been planning on Thursday to use a helicopter on board the Snow Dragon — which is waiting at the edge of the ice pack with the Aurora — to rescue 52 scientists and tourists, a dozen at a time, over five hours. All 22 crew members are expected to stay with their icebound vessel, which is not in danger.

The passengers were then supposed to be flown 11 kilometers (7 miles) to the Chinese ship, from where they would be transported 4 kilometers (2 miles) by barge to the Australian icebreaker. They were then expected to travel to the Australian island state of Tasmania, arriving by mid-January.

Earlier Thursday, it appeared likely the rescue would go ahead, with expedition leader Chris Turney posting a video on his Twitter account, blue sky visible behind him.

“A stunning day,” he said on the video. “Hopefully we’ll hear about the evacuation soon.”

The Akademik Shokalskiy, which left New Zealand on Nov. 28, got stuck Christmas Eve after a blizzard pushed the sea ice around the ship, freezing it in place about 2,700 kilometers (1,700 miles) south of Hobart, Tasmania. The ship isn’t in danger of sinking and has weeks’ worth of supplies on board, but it cannot move.

The scientific team on board had been recreating Australian explorer Douglas Mawson’s 1911 to 1913 voyage to Antarctica. Turney had hoped to continue the trip if an icebreaker managed to free the ship.