The
way a plane
is able to fly is the force of lift. Now the way a wing is constructed
is the top side of the wing is raised while the bottom side is flat.
The wind that is going
against the wing has to bypass it by either the top side or bottom
side. The air flowing above the wing moves at a faster rate than the
bottom because it travels a greater distance. Because the wind is
moving faster, there is
a greater pressure pressing up under the wing, than pressure pushing
down on the wing, causing lift.
Now the problem with the flight of the X-Wing in space, or any spacecraft for that matter, there is no air to have a force on. With planes, they have flaps, rudders, spoilers, elevators, etc. to act on this force to make it bank and turn as your have seen whether you have been to an air show, seen planes in the air, or have rode on one. Even though these spacecraft look like it can fly within our atmosphere, it serves no aerodynamic purpose.
As you can see in this clip how these spacecraft actually fly, the only way this could be possible is if the spacecraft had many little jets on the surface of the craft. According to Newton's 3rd law, every action has an equal and opposite reaction, each of these little jets could shoot out a mass that apply a force on the craft to make it maneuver that way they do in this clip. Its is fesable, but not very practical, and the spacecrafts in Star Wars would not look as pretty as they do in the movie.