Rotating aircraft engine components are subject to transient combine high cycle and low cycle fatigue loading (HCF/LCF) as resonances are crossed during throttle excursions.  Current design practice is to assume a component's fatigue life has been expended once a crack is large enough to grow under such conditions.  However, such an assumption may be unrealistically conservative in a prognosis framework were a high fidelity prediction of the actual useful life is required.  This paper describes a simulation capability that has been developed to model fatigue crack growth under HCF/LCF conditions.  It combines the FRANC3D/NG program to adaptively modify finite element meshes to simulate crack growth and the VICTER program to perform reduced order vibratory analyses of components with cracks.