Future aircraft are expected to have a high level of fuselage-engine integration, exposing the propulsor to non-uniform inflow conditions, in which the performance and stability of the engine fan can be severly affected. This paper proposes a study of a transonic fan subject to inlet distortion by employing steady RANS simulations and mean line calculations. The steady CFD results, although insufficient to correctly measure the interaction of the distortion across the cascade passages, are used as a benchmark to compare the prediction of a leaner low-order tool, adopting a superposition of several 1D calculations in the discretised compressor approach. A continuous total pressure deficit is imposed at the inlet and the distorted operating points are compared to the clean inflow case. The performance drop at the peak efficiency point is similar for the two models, altough the mean-line 1D method fails in closely matching the distribution in the upper span of the blade. The qualitatively similar response of the low-order approach to the distorted inflow should allow for its use in preliminary blade design exploration once improved for high-speed flow prediction.