Abstract: A turbofan exhaust nozzle apparatus includes: an inner shell having a centerline axis, the inner shell disposed inside a surrounding outer shell to define an annular flow duct therebetween terminating in an outlet at a trailing edge of the outer shell, the inner shell terminating in a trailing edge aft of the outlet; and a pylon interrupting circumferentially the duct; wherein an aft portion of the outer shell is non-axisymmetric around a common centerline axis of the nozzle, and the trailing edge of the outer shell is vertically non-coplanar.