A modified Reynolds equation including centrifugal force of gas film was derived, and it was used to study the effect of gas film centrifugal force and associated streamline on the load capacity of both rigid and foil thrust bearings operating in hydrodynamic and hybrid modes. The thrust bearings have six pads with an outer diameter of 82 mm and an inner diameter of 47 mm with typical aper-flat geometry. The setup for the simulations is a single-acting air thrust bearing operating at various ambient pressures and isothermal temperature. Air was chosen for the gas film for the investigations, but the modified Reynolds equation can handle any general gas films through nondimensional parameter governing the centrifugal force. The simulations were performed with varying ambient pressure from 1 to 9 bar. The simulation results at different ambient pressures and temperatures are presented in forms of pressure profiles, streamlines, and bearing's load capacity. The bearings' load capacity becomes worse when the centrifugal force is considered at very low temperature, and the reduction of the load capacity grows more noticeable with the increase of the ambient pressure and the decrease of the ambient temperature. However, at higher temperature where centrifugal force is not large enough to create large leakage, the centrifugal force helps to redistribute the streamline to favorable way to increase the load capacity.