Could have been a mountain wave that pulled him in. clear air turbulence and wind shear created a stalled condition or some sort of catastrophic failure of the air craft. There may have been medical conditions, hypoxia, heart attack. There rarely is just one factor in an aviation indecent. Additionally everything here is speculative. Here are the facts. Steve Fossett is missing. His aircraft and personal belongings has just been found and there is human remains near or in the crash zone. Most probable the human remains are Steve Fossett.