Shelter
Shelter is critical for preventing hypothermia, one of the greatest dangers in the wilderness. A shelter can be constructed from aircraft debris or branches and leaves. A barrier fashioned from seat covers, leaves, etc. should be placed on the ground to prevent heat loss when lying down.
Snow caves can provide very effective makeshift shelters. Scraping away the snow on the floor down to the bare earth will increase the temperature inside by about 12 degrees. Lighting a candle will increase it by another 4 degrees.