Elastic-plastic deformation mechanics ahead of the curved fronts of planar fatigue cracks in CCP specimens of Al 2024 was modeled using FEM. The results are discussed in light of the immediate local front rate estimations which are based on the strain energy accumulation analysis. The comparison of the theoretical model with experiments shows that the critical strain energy density to local fatigue fracture is not a material constant. The critical energy density generally depends on both the distance from the free surface and the crack length.