Abstract: A method of generating a multifidelity model of a system comprises the steps of obtaining training data from a high fidelity model of the system, providing a low fidelity model of the system, providing a kriging model to compensate for discrepancies between the high and low fidelity models, adjusting the kriging model to maximise the likelihood of the training data when the low fidelity model, compensated by the kriging model, is used to model the system, and generating a multifidelity model of the system based on the low fidelity model when compensated by the adjusted by the adjusted kriging model. The system may be a gas turbine or a part of a gas turbine for example a tail bearing housing.