A review is given on the status of reduced order modeling of unsteady aerodynamic systems. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic flows, a large, sparse eigenvalue is solved using the Lanczos algorithm. Following this, a Reduced Order Model of the unsteady flow is constructed. As an alternative to the use of eigenmodes, Proper Orthogonal Decomposition (POD) is also considered.