The transonic regime is of great interest for designing aircraft wings because most conventional aircraft fly transonic. When flying in this regime, the wing of the aircraft tends to experience a phenomenon known as buffet, which is characterized by an oscillating shock wave. The surface pressure of a structure experiencing transonic flow is always changing; however, the average surface pressure can be computed. Pressure sensitive paint (PSP) is a flow measurement technique that determines the surface pressure and serves to compute its average. Using PSP, the average surface pressure of an ONERA OAT15A supercritical airfoil model can be determined in transonic conditions. This allows to study the effect of shock control bumps on the shock wave and surface pressure of the OAT15A model, as well as to determine the pressure coefficients of the airfoil.