The Blended Wing Body (BWB) configuration seems to be one of the most promising concepts to replace the current passenger transport aircrafts with substantial improvement of their performance and reduction of their environmental footprint. However the expected gains still need to be precisely evaluated with airplanes to design. BWB concept is a highly coupled system because every sizing discipline is connected to a single system: the wing. This paper presents the multidisciplinary design analysis and optimization process of a blended wing body and its application to a long-haul commercial transport mission.