The criteria that are required for an aircraft to be longitudinal statically stable, is:

► To have a nose-down pitching disturbance that is used to produce the aerodynamics forces to give a nose-up restoring moment.

► This restoring moment that is produced should be large enough to return the aircraft to its original position after the disturbance.

► The requirements are met by using the tail-plain that is horizontal stabilizer used to provide the stability to the aircraft.