The feasibility of operating a mainshaft thrust bearing at high speeds with jet fuel mist as the coolant and lubricant has been demonstrated in both rig and engine testing. A split-inner ring hybrid thrust bearing ( silicon nitride balls ) was successfully operated to 1.67 x 106 DN at maximum Hertzian contact stresses up to 322,000 psi. The bearing configuration also included BG-42 inner and outer rings and a Dupont polyimide Vespel separator. The incorporation of a fuel lubrication system for limited-life turbine engines has many advantages, including; Lower cost ( elimination of oil system related hardware ). Enhanced long-term storage reliability Increased cold start reliability. The bearing has been subjected to a variety of hostile tests, including; Snap accelerations from -65 deg F cold soak Extended operation at similar thrust and radial loadings Operators at high thrust levels thrust levels This paper describes the development history, including rig and engine testing, as well as the analytical challenges overcome in designing the hybrid configuration.