elsA is a multi-application CFD simulation platform dealing with internal and external aerodynamics from the low subsonic to the high supersonic flow regime. The compressible 3-D Reynolds averaged Navier-Stokes equations for arbitrary moving bodies are solved by a cell centered finite-volume method with second order upwind or central space discretization with scalar or matrix artificial dissipation on multi-block structured meshes. A high flexibility in the multi-block approach is achieved in elsA through patched grid, Hierarchical Mesh Refinement and Chimera techniques. The discrete equations are integrated either by multistage Runge-Kutta schemes with implicit residual smoothing, or, which in general leads to a better efficiency, by backward Euler integration with implicit LU schemes. For time accurate computations, the implicit dual time stepping method or the Gear integration scheme are employed. Preconditioning is used for low speed flow simulations. A large variety of turbulence models are available, ranging from eddy viscosity to full differential Reynolds stress models, and including options for Detached Eddy Simulation (DES) and Large Eddy Simulation (LES). Various transition models are also available for complex geometry configurations. elsA software package includes an important software module dealing with aeroelasticity [8], [9]. Also, a module dealing with calculation of gradients by linearized equation or by adjoint solver techniques is very useful for aerodynamic optimization.