An airplane wing has a very specific shape, designed specifically to have more surface area on top of the wing than on the bottom. Because there is more surface area on the wing's top, as the wing moves forward, air is forced to flow over the top of the wing at a faster rate than it flows over the wing's bottom. This difference in air flow creates a small area of vacuum just over the top of the wing; this vacuum is what generates the necessary lift to get the airplane off the ground.