This chapter describes the use of computational fluid mechanics at Dassault Aviation. A historical perspective gives a measure of the successive giant steps that have been made over the past 30 years. A rather detailed description of industrial codes leads to a good understanding of the key numerical concepts assembled to create a powerful tool for computational aerodynamics. The fundamental issue of turbulence modeling is addressed in detail. A large range of complex applications is described to illustrate the variety of problems solved. The status of the development and application of shape optimization techniques and multidisciplinary design are finally illustrated.