The S-shaped air intakes are very common shapes due to their ease in the engine-body integration or Radar Cross Section, RCS, specifications especially for fighter aircrafts. The numerical shape optimization of an S-shaped air intake using adjoint method is conducted. The flow of a specified air intake that uses S-duct M2129 is simulated using three dimensional (3D) numerical solution of Reynolds-Averaged Navier-Stokes equation along with k-ω SST turbulence model. The main purpose of this optimization scheme is to maximize the total pressure recovery (TPR). Further, the scheme is developed in such a way that would be applicable in industry thru satisfying specified constraint requirements. The cross sectional areas of the geometry of duct inlet and outlet (known as engine face) remain unchanged. In addition, small shape modification in each optimization step is considered. Finally after nine optimization cycles new S-shaped air intake geometry with higher TPR and lower distortion (DC) is generated, that would achieve higher performance during its operation.