I find it funny how in space battles/travel/everything, there is always a definite up and down; all the ships obey this rule and are rotated the right way, and solar systems are like a 2-D plain. Movie space battles are like those of submarines; you can move in any direction, but there is always a definite up. In real space, there wouldn't be, and ships would enter battles with their cockpits all facing different directions.
Solar systems are in a flat plane usually in real life, actually. It's becasue they form out of rotating balls of gas, and a rotating object only has one axis.