JAXA (Japan Aerospace Exploration Agency) has been conducting a research on a future commercial tilt wing VTOL (Vertical TakeOff and Landing) transport under JAXA's "Sky Frontier" Program aiming to develop technologies for aircraft innovation. The research focuses on QTW (Quad Tilt Wing) civil VTOL transport, which features tandem tilt wings with propellers mounted at the mid-span of each wing. The goals of the research in the present phase are to propose a concept of a QTW business VTOL transport system and to pursue the essential technologies development such as OEI (One-Engine-Inoperative) safe recovery, transition flight control and cruise efficient aerodynamic design. Nine passengers business QTW concept was designed and trade-off analysis of the propulsion system architecture for OEI safety was conducted. The result suggests the architecture having no cross-shaft mechanism with auto-failure-compensation is the most effective in terms of the system weight and operating cost. Controller design technology for full-envelope auto-guidance mode has been developed and a series of flight evaluations has been started using a small QTW UAV (Unmanned Aerial Vehiclde) demonstrator. A CFD (Computational Fluid Dynamics) tool for cruise efficient tandem wing design has also been developed and its preliminary validation has been conducted. This paper summarizes the overview of the research program and the current progress of the system concept design and the essential technology research.