The present work presents the numerical investigation of the bump height manufacturing errors on the unbalance response of an aerodynamic foil journal bearing. This is the first study of the impact of manufacturing errors based on an important number of samples. A statistical analysis predicts the mean values of the characteristics and the standard errors of the mean. The paper presents the most important aspects of the numerical model that was used and the way it was implemented for the unbalance analysis of a four degrees of freedom rotor. It was considered that the bump height manufacturing errors had a normal distribution (i.e. each bump had a different random height) around the design (mean) height value. The standard deviation of the bump heights (the same for all bumps) is a measure of the magnitude of the manufacturing errors. The results give a qualitative but above all quantitative overview of the impact of machining errors on some characteristics of aerodynamic foil bearings.