Residual fatigue lifetime assessment of a cracked structure is a common task for engineering and scientific community. Fatigue crack may appear on the surface or in the initial defect, e.g. pores in weldments. Such a structure needs to be examined, whether is it safe to be operated. Various assessment methods of different difficulties exist. In this paper, numerical and experimental study on fatigue crack propagation is presented. Propagation of a fatigue crack starting from an initial surface defect of semi-elliptical shape through the flat specimen is considered. Two load ratios were employed in order to compare their effects, as loading at low asymmetry R = 0.1 ensures presence of a plasticity induced crack closure, while at load ratio R = 0.6 fatigue crack growth without premature closure is expected. Beach marks were created on the fracture surface in order to study the fatigue crack evolution, number of cycles spent for fatigue growth and also the influence of premature closure on the crack front evolution. One of the well-known methods was applied for numerical fatigue lifetime evaluation and estimated number of cycles required for crack growth through the body was compared to the experimentally measured data. Second part of the paper deals with fatigue crack front curvature, which is always affected at the vicinity of the free surface due to the corner singularity of the stress field. However, when crack closure appears, fatigue crack propagation is retarded and furthermore, crack front is curved even more at the free surface as a result of earlier closure than in the middle of the body. Separation of these two effects allows direct comparison of their impact on fatigue crack front propagation.