well, my flying enemies are quite simple.
It is for a 2d platforms game style, and I'm talking about enemies that just fly around with no colisions with walls or anything. I just want it to fly in a way you don't see any straigth movement (I mean, not in lines, but in circular motion when its direction changes).

I did a very simple test telling the enemy to go go in direction of main character, and only change direction if it passed the main character by more than 100 pixels, for example, following straight lines in X and Y, but with acceleration in both axes. this way it looks like cirular motion when it changes direction!! Too easy, but too good also,