I have acrophobia and have occasionally heard, or known by myself, that it was often more a fear of jumping than of falling. Wiki and Google do not confirm this; they mention a different phobia (Catapedaphobia) but it doesn’t seem right either.
I also get the sensation Cheshire Human mentions but, fortunately, it’s just a light fantasy not a disabling fear.
I don’t fear heights riding airplanes … except (slightly) when next to emergency door!