The ski of an Air National Guard LC-130 Hercules aircraft sunk into snow that bridged a hidden crevasse as the plane taxied for take-off on Nov. 16 from a glaciology research site in the West Antarctic Ice Sheet.

None of the seven crew members and four passengers onboard the plane was injured. The $45 million plane remains at the Upstream D field site, 80 miles southwest of the Siple Dome camp, lodged in a crevasse that is estimated to be about 10 feet wide and "deep and dark," said Col. Rich Saburro, commander of Operation Deep Freeze. The crevasse had been bridged by more than 8 feet of snow, making it nearly impossible to detect.

"There was no way you could see this," said Col. Graham Pritchard, 109th Air Lift Wind Commander, based in Schenectady, N.Y.

Those onboard weren't sure what had happened when they felt the plane tilt from one side to the other and then stop. "At first I didn't realize it at all," said Herman Engelhardt, a passenger and researcher with the Upstream D science project. "It was a very slow motion. Nothing at all dramatic."

Passengers and crew members evacuated the plane out the cockpit escape hatch and walked out on the wings to stay clear of the unstable area immediately around the crevasse opening.

With all involved safely transported out of the area via a twin-otter aircraft, the Air National Guard and McMurdo Search and Rescue mountaineers are now focused on evaluating the site and creating a plan to recover the 110,000-pound plane. Experts from Robbins Air Force base in Georgia have also been called in because of their experience retrieving planes from around the world in every kind of accident situation.

However, Pritchard said, "This might be the first time they're recovering one from a glacier in Antarctica."

One possible recovery plan involves placing large air bags under the plane to lift it. Special devices would then be harnessed to the body of the plane before it is pulled out by a bulldozer.

To get a vehicle of that size to the site and near the opening of the crevasse will require several LC-130 landings at Upstream D. The area is laden with crevasses, and a team of investigators and mountaineers are searching for a safe landing site.

Due to the varied movement of the ice stream, which can be 10 to 100 times faster than the surrounding ice, enormous crevasse areas called shear margins form in the middle of these big stream zones. Despite the hazards of the area, National Science Foundations representative Simon Stephenson said there was "promising" information from a recent fly-over of the site that there may be a safe spot.

The impact on this season's NSF science projects and South Pole reconstruction also looks promising. The Air National Guard, which owns the incapacitated plane, will send another LC-130 to McMurdo as a replacement. The plane should be in McMurdo by Nov. 27, Pritchard said.

That concern behind him, Stephensen is looking ahead for more answers about the aircraft incident. "The main concern must be how did it happen and how can we make it very unlikely that this happens again?" Stephenson said. "The last time we drove an airplane into a crevasse was in 84. That was a long time ago."

This was the first time an LC-130 had landed at Upstream D, and the Air National Guard has initiated an investigation to find out what it can do to reduce the chances of this kind of accident happening again.

Knowing the difficulties involved, the Air National Guard began preparation for this flight six months ago by reviewing satellite images and aerial photographs. On the day of the flight, visual observations were made by a crew with more than 100 years of combined experience flying in Greenland and Antarctica. Even with many hours spent studying the area, Stephenson said there are no givens in the unpredictable land of the Antarctic.

"There's always a potential for surprises," Stephenson said. "Anytime we go to a new site, we're probably at a little bit higher risk."

But, merely blaming the accident on the risks of doing business in Antarctica is not always the right answer, Stephenson said.