A large-order modal analysis capability has been incorporated in the Aeroelastic Design Optimization Program (ADOP). This module includes an accelerated sub-space iteration scheme with modifications to the numerical error correction technique and some improvements in computational efficiency. Special considerations are presented for solving large size problems, such as a set of equations stored in an envelope format, large matrix blocking, finite-element node renumbering, and automated structural model correction. Rigid body modes may be computed independently of the modal analysis to reduce the cost of the eigenvalue solution. Small and large numerical examples are presented to demonstrate the effectiveness of the modal analysis technique.