The flow over a rectangular cavity is predicted using the Spalart-Allmaras turbulence model and two versions of Detached Eddy Simulation (DES). The cavity geometry is the Weapons Internal Carriage Separation (WICS) cavity bay with a length-to-depth ratio of 4.5. Statistical and mean properties of the solution are compared with experimental mea- surements at freestream Mach number 0.95 and freestream Reynolds number 2:47×106/ft. Flow visualizations show the oscillating shear layer induces small regions of supersonic flow that travel downstream past the cavity trailing edge. These small regions also interact with the streamwise vortices that develop due to the interaction of the oscillating shear layer and cavity sidewalls. Mass is ingested into the cavity as the shear layer impinges on the downstream wall and recirculates to the upstream wall via interaction with the vortical structures resolved in the cavity. Predictions using the newer DES version, De- layed Detached Eddy Simulation,1 are in slightly better agreement with measurements of mode shapes compared to the original version of the method. Time-averaged pressure distributions along the cavity centerline show the original DES formulation compares well with measurements whereas the modified formulation overpredicts the pressure on the downstream half of the cavity.