So how do the lucky one-in-four survive? The answer, surprisingly, is that a few factors of human physiology are at play: As the aircraft climbs, the body enters a state of hypoxia—that is, it lacks oxygen—and the person passes out. At the same time, the frigid temperatures cause a state of hypothermia, which preserves the nervous system. “It’s similar to a young kid who falls to the bottom of an icy lake,” says Roman. "and two hours later he survives, because he was so cold."