How do victims die in an airplane crash?

My girlfriend passed away a while ago in one and last night I had a rather violent dream about it. I'm sure (or hope) that victims don't die that way, but now I'm wondering how they DO meet their demise.

In my girlfriends case specifically, the pilot overshot the runway, crashing into a valley because there was no runway left. It isn't exactly plummeting out of the sky, but the pilot probably attempted to abort the landing so I'm assuming the plane was at takeoff velocity. Assuming there was no instant fire, what happens physiologically on impact at that speed?