Gravity is the downward force which tends to draw all bodies vertically toward the center of the Earth. The airplane’s center of gravity (CG) is the point on the airplane at which all weight is considered to be concentrated. For example, if an airplane were suspended from a rope attached to the center of gravity, the airplane would balance. 

The center of gravity is located along the longitudinal centerline of the airplane (imaginary line from the nose to the tail) and somewhere near the center of lift of the wing. The location of the center of gravity depends upon the location and weight of the load placed in the airplane. This is controlled through weight and balance calculations made by the pilot prior to flight. The exact location of the center of gravity is important during flight, because of its effect on airplane stability and performance.