The ability of controlling a flow field to obtain a desired change is of great importance. In this work I have studied air flow control through an aircraft's inlet device. To observe the effect of creating an auxiliary inlet in the side of the inlet device I’ve studied first an one-dimensional compressible flow through a pipe with variable section and with an auxiliary inlet. By varying the position of the auxiliary inlet I’ve analyzed the effect of suction/injection of fluid through this inlet upon the flow through the pipe. Further on I’ve studied the air flow through the inlet device of a supersonic aircraft at take-off conditions. In these conditions along the inlet device occur considerable total pressure losses. To reduce these losses I've created an auxiliary inlet in the side of the inlet device through which to take place an outside air injection. The purpose was to find a relationship between the medium total pressure at the compressor's entry and the opening of the auxiliary inlet knowing that at the the compressor's entrance the Mach number of the air flow must be 0.5.