Half a century after Northwest Airlines Flight 4422 slammed into the side of 4,950-meter Mount Sanford in eastern Alaska's Wrangell Mountains, killing all 30 men on board, commercial pilots Kevin McGregor and Marc Millican found the wreckage embedded in a glacier. After searching fruitlessly for the debris from the air, McGregor and Millican undertook several arduous treks on foot on the glacier. Watch this slide show to see some of the photos McGregor took during the climbs, and hear him talk about the quest to find the wreckage of NW 4422.

McGregor and Millican faced such dangers as sudden snowfall, grizzly bears and hidden crevasses in the remote backcountry. On one of their visits to the site after locating the wreckage, they found a severed human arm complete with its hand embedded in the ice. Read about the scientific challenge of identifying the remains in "Arm in the Ice" by Colleen Fitzpatrick (preview) in the December 2011 issue of Scientific American.