Years ago, I worked with a guy who had an additional duty as an accident investigator for the USAF. He told me that most crashes happen during take-off or landing (except deliberate crashes like 9/11 or rare in-flight explosions like TWA 800). The impacts themselves are quite survivable. What kills people who survive the impact is the smoke/fire afterwards. People who don't survive the impact (his experience with USAF fatalities where the aircraft was generally intact) generally die from the deceleration G Forces when the aoerta rips away from the heart and they bleed to death.

I've read somewhere that commercial airliners were designed to permit a total evacuation from an intact airliner within 90 seconds from any seat in a fully-filled cabin. I think all of us know that's a complete joke. So, I figure that if I survive the impact, I'll take a deep breath of superheated air and get it over with quickly.