This study presents the numerical investigation of three-dimensional fluid structures that develop as air flows around an infinitely long inclined flat plate. Detached Eddy Simulation (DES) is performed at a Reynolds number of 1.57×10⁵ based on the width of the plate and the approaching flow velocity. Vorticity contours on the two-dimensional plane at the midspan of the plate show that spanwise vortices shed from the inclined flat plate and quickly dissipate in the downstream wake. The three-dimensional iso-surface of λ₂ shows the presence of streamwise vortices that develop along the braid of previously shed spanwise vortices. The spanwise wavelength of the streamwise vortices ranges from 1.36 to 1.86 times the width of the flat plate, which lies in the range corresponding to the mode B instability in wake transition defined in previous studies. The streamwise vortices get trapped between the spanwise vortices and induce instability in the spanwise vortices and the shear layer.