I have had lucid dreams where I can fly easily and others where I have to flap my arms or even swim to keep aloft.
My personal take on it is that it has to do with energy/vibration rates. Some as you go deeper inside your consciousness into these planes, the "density" of the planes gets less and less. So things like flying may get harder to do till you balance out into that plane.
but thats only my pet theory on it
Expecting life to treat you well because you are a good person is like expecting an angry bull not to charge because you are a vegetarian. - Shari R Barr