We describe our massively parallel finite element computations of unsteady incompressible flows involving fluid-body interactions. These computations are based on the Deforming-Spatial-Domain/Stabilized-Space-Time (DSD/SST) finite element formulation. Unsteady flows past a stationary NACA 0012 airfoil are computed for Reynolds numbers 1000, 5000 and 100 000. Significantly different flow patterns are observed for these three cases. The method is then applied to computation of the dynamics of an airfoil falling in a viscous fluid under the influence of gravity. It is observed that the location of the center of gravity of the airfoil plays an important role in determining its pitch stability. Computations are reported also for simulation of the dynamics of a two-dimensional ‘projectile’ that has a certain initial velocity. Specially designed mesh moving schemes are employed to eliminate the need for remeshing. All these computations were carried out on the Thinking Machines CM-200 and CM-5 supercomputers, with major speed-ups compared to traditional supercomputers. The implicit equation systems arising from the finite element discretizations of these large-scale problems are solved iteratively by using the GMRES update technique with diagonal preconditioners. The finite element formulations and their parallel implementations assume unstructured meshes.