Flapping wing miniature air vehicles (MAVs) have significant potential in surveillance, search, rescue and reconnaissance applications. These applications require the MAV to carry payloads in the form of batteries, on-board cameras, camera, sensors etc. In order to ensure that the payload capacity of the MAV is maximized for a given wing area and flapping frequency, we need to carefully design the drive mechanism to reduce its mass and ensure that it meets the intended functional requirements. The overall design approach described in this chapter incorporates the advances in modeling and simulations methods in kinematic and dynamic analysis, finite element analysis, and manufacturability analysis. We demonstrate applicability this design approach using two case studies.