The focus of this paper is on the identification of nonlinear reduced order models for the prediction of the geometrically nonlinear structural response of cantilevered structures, including the wing of the Predator. These models represent the extension to large displacements/rotations of the modal models used in the linear range. The identification of their coefficients is carried out here from a full finite element model of the structure in a commercial software, Nastran was used in the present effort. Issues encountered in the past in successfully carrying out this identification are revisited and clarified. The development of a nonlinear reduced order model for the Predator is then performed and validated demonstrating the capabilities of these reduced order models in connection with complex structural models.