I've flown as a commercial pilot for many years and have volunteered as a Company Safety Officer. As such, we were trained by the National Tranportation Safety Board (NTSB here in the U.S.) as well as the FAA in accident investigation. One of the first things learned is that the human body, under the right conditions can survive "G" loads as high 17 or so. In major high speed types of crashes the "G" loads experienced can exceed 100 although 30 to 50 are common. This means a 150 pound man or woman will weigh, at the nano-second of impact, more than 7,500 pounds at a 50 G deceleration. The now deceased body is often restrained by the seat belt or other obstructions, but the clothing continues on due to inertia. Alternately, the body flies through the cabin and is denuded by seats, other passengers and bulkheads. I've found fully functioning passenger seats, upside down and when moved to upright position displays a body in what could only be described as a placid, asleep looking state. We have also found cellular phones 200 feet away from the body to which it belonged. This is due to the weight of the phone being in a compact, dense mass and tears its way out of the person's shirt pocket or belt holster.
We have investigated accidents wherein the aircraft struck the ground in a relatively flat position and little damage was noted to the fuselage. However, after removing interior wall and ceiling coverings, our metallurgist demonstrated that the cabin had been compressed from a normal 7 foot height or so, down to less than 2 feet and then sprung back to its original size, all in the space of about 1/1000th of a second... Very interesting once one gets past the human tragedy involved...