The airframe/propulsion integration for supersonic airliners was studied considering three engine layouts (i.e., under-wing, over-wing, and side-body engines). In this study, the engine position was optimized for each layout from viewpoints of low-drag, low-boom, and high-range performances. This study revealed that the interference between nacelle shock wave and wing is important to achieve low-drag and low-boom, and that side-body engines realize the best compromise between them by setting engine so that the nacelle shock wave acts on the rear part of the wing. The engine position affects the inlet aerodynamic performance, which in turn affects the range performance. However, the side-body engine remains optimum, even when the range performance is taken into account.