From what I understand, you experience that "butterfly" feeling due to the acceleration of the roller coaster (for instance). However, when you jump out of an airplane you are already going at terminal velocity, so you don't speed up any upon exit, thus no butterflies.
hope this helps. and I think that the best way to describe the free fall feeling is floating. Imagine laying on your back in a pool not moving...just floating. That is what it feels like to me, except you are face down for most of it....hehe. "A woman is like a tea bag; you never know how strong she is until she gets into hot water" ~ Eleanor Roosevelt ~