Unsteady transonic Lattice Boltzmann simulations of the NASA Common Research Model in the European Transonic Windtunnel are presented. Modelling of the slotted wall transonic test section is described and different simulation approaches are discussed. Quantitative comparisons are performed using data obtained for the NASA Common Research Model at its design point and at off-design conditions. Good qualitative and quantitative agreement between simulations and uncorrected experimental measurements are shown. A preliminary comparison between wind tunnel and free-air simulations is also presented and shows promising correlation to the wall interference corrections applied to the measurements.@en