Research is proposed for the development and implementation of state of the art, reduced order models for problems in nonlinear aeroelasticity. Highly efficient and accurate aeroelastic simulation tools will be constructed based upon the mathematical formalism of optimal prediction theory and a novel implementation of a filtered harmonic balance solution methodology. The implications of the proposed work include orders of magnitude reduction in computational time, with minimal loss of accuracy, for time periodic problems in nonlinear aeroelasticity. The application of the proposed innovations spans the range of flight, from high-speed transport vehicles, to small-scale, flapping Micro-Air vehicles. Anticipated results include 1) the implementation of the proposed reduced order methodology into both a standard grid-based aeroelastic tool and a material point method monolithic aeroelastic solver for the production of technology ready, multi-flow regime aeroelastic simulation tools 2) application of the proposed work to large-scale simulation and comparison with experiment and "full-order" aeroelastic simulations and 3) advancement of the state of knowledge for nonlinear problems in aeroelasticity in both the subsonic, low Reynolds number regime and transonic high Reynolds number regime.