Abstract: The development of perturbations of rotational velocity of rectangular prisms in air flow at low Reynolds numbers is analyzed using the curved body hypothesis. Undisturbed motion is rectilinear motion in a direction perpendicular to the prism’s generatrix. The development of perturbations of transverse velocity of prisms is studied using the quasi-stationarity hypothesis. The Navier–Stokes equations are solved by the finite volume method using the freely distributed SU 2 software package. The behavior of prisms with different aspect ratios of their transverse rectangular cross-sections is investigated. It is found that rotational velocity perturbations develop if the aspect ratio is less than 10. Translational transverse velocity perturbations develop if the aspect ratio is less than 3.