LMAO. Ok that is just about as funny as it gets right there.

Here's a did you know question. Did you know that every seat on 99% of all commercial aircraft actually floats? Some better then the provided life vests.

And to get back on topic, as dynamo stated altitude is also a killer not only with the lack of oxygen but also the temperature.

Still with the parachute how do you plan on making it passed the wings and engines? Oh and the horizontal stabilizer?

Here is some basic information if you actually care to check it out:
http://www.tc.faa.gov/its/worldpac/techrpt/ar03-32.pdf

Even jumping out the rear of an airplane, unless it is a prop / turbo-prop, you will still be affected by the extreme temperatures of jet blast.

Also what about the panic inside the plane as everyone races to get their parachute, put it on, get the doors open and leap. That would be some insane madness right there. Chad I suggest some roids (not really) to bulk up to mow some suckas down.