Another potential benefit of winglets is that they reduce the intensity of wake vortices.[11] Those trail behind the plane and pose a hazard to other aircraft.[12] Minimum spacing requirements between aircraft operations at airports are largely dictated by these factors. Aircraft are classified by weight (e.g. "Light," "Heavy," etc.) because the vortex strength grows with the aircraft lift coefficient, and thus, the associated turbulence is greatest at low speed and high weight, which produced a high angle of attack.[citation needed]