The report summarizes the work on computations of a weapons-bay flow in the framework of the FoT25 project "Studier av inre vapenutrymme". Numerical simulations were conducted for the FS2020 aircraft model at a Mach number of M1 = 0.9 and an angle of attack of = 9o. A weapons bay was embedded in the front part of the aircraft fuselage. One of the main purposes with the computational investigation was to highlight the general features of the flow around the aircraft, with a focus on the unsteady flow properties over and inside the weapons bay and, consequently, to explore its potential aerodynamic effect on the aircraft and on the store placed in the bay cavity at different locations. In the first part of the work, computations were carried out for a half-body configuration with no store, using steady RANS, DES (detached eddy simulation) and hybrid RANS-LES approaches. The emphasis was placed on the analysis of unsteady flow features over the weapons bay, for which the DES approach and a hybrid RANS-LES modelling method were invoked. Besides a baseline grid, a refined grid was also employed to highlight the effect of grid resolution. The resolved instantaneous flow motions past the bay cavity were illustrated with the results from the DES and hybrid modelling. Comparison of different modelling approaches were made for the time-averaged (mean) flow properties in terms of the flow pattern, pressure distributions and integrated forces. An analysis was also conducted for the pressure fluctuations on the weapons-bay cavity wall surfaces. On the basis of these computations, the second part of the work consisted of a numerical investigation on the aerodynamic flow when a missile model was stored in the weapons bay at different locations. A whole-body configuration was used in the simulation. The aerodynamic effect on the missile was explored. In order to diminish the large nose-up pitching moment on the missile model, the flow-control effect of a spoiler mounted on the bay leading edge was also highlighted in RANS computations.