Drag is a design parameter of primary interest in aerodynamics performance evaluation. Its accurate prediction and phenomenological decomposition can provide a valuable physical insight into its origins, and also gives a basis for aircraft design improvements or optimization. In addition, thrust/drag bookkeeping is of primary interest in aircraft design for the decomposition of the airframe and engine contributions to overall aircraft performance. Nevertheless, for innovative configurations such as highly-integrated aero-propulsive concepts this decomposition may be difficult. The above have motivated the investigation of several theories and approaches for drag analysis and decomposition over the last century. The present paper gives an overview of ONERA methods dedicated to the analysis of drag, both from computational fluid dynamics simulations and wind tunnel experiments.