While others may say you don't need separate shelter, please consider that if you go down in the mountains, your airplane may reach the ground but your parachute will probably be hung up in trees 30 or 40 feet over your head. And don't expect the aircraft to provide shelter. It will most likely be leaking fuel and pitched at an unuseable angle once it hits the ground. And, aluminum is not a great shelter even in the best of times. It gets very cold, very quickly.