Shipborne wind speed measurements are relevant for field studies of air–sea interaction processes. Distortion of the airflow by the ship’s structure can, however, lead to errors. We estimate the flow distortion bias by comparing the observations to ERA-5 reanalysis data. The underlying assumptions are that the bias depends only on the relative orientation of the ship to the wind direction and that the ERA-5 wind speeds are (on average) representative of the true wind speed.