Variable area fan nozzle stiffeners and placement

A nacelle assembly for a high-bypass gas turbine engine is disclosed and includes a variable area fan nozzle (VAFN) (45) including at least one second fan nacelle section (42) movable relative to the first fan nacelle section (40) to modify an area of the bypass flow path (50). At least one stiffener (64) is mounted between the first fan nacelle section (40) and the second fan nacelle section (42). The stiffeners (64) modify mode shapes and natural frequencies to substantially reduce or eliminate flutter within operating ranges that are produced by unsteady aerodynamic loads.