Abstract: CFD gradually plays an increasingly important role in aircraft design and turns out to be the major method at present. One of the most famous and successful tools is TRANAIR, which has been a workhorse tool for Boeing aerodynamic design for more than a decade. Industry has quite strict demands on CFD tools, including better computing efficiency, accuracy, convenience and robustness. To meet these requirements, Beijing Aircraft Science and Technology Research Institute (BASTRI) of China Commercial Aircraft Corporation (COMAC) has developed an in-house code, named as SUN code, which could automatically generate body-fitted structured overset mesh, with grid projection method originally proposed by the author, for aircraft configurations composed of any number of fuselage, wing, pylon and nacelle type components and analyze the steady flow based on inviscid-viscous coupling method. The distinguishing feature of SUN code is that the process of pre-treatment, mesh generation, flow analysis and post-treatment is fully automated.