A system for monitoring occupancy of a seat arranged in a transportation vehicle is disclosed. The system includes at least one detection device arranged in the vehicle, within the seat or near the seat, and at least one centralized occupancy management system located outside of the vehicle and at least one occupancy management system located outside of the vehicle. An occupancy displaying unit is arranged on the seat or next to the seat for providing visual information about seat occupancy. The passenger's mobile communication device is used by the system for locating the passenger inside the transportation vehicle, by means of dedicated device detection units arranged in the transportation vehicle. The centralized occupancy management system and the occupancy management system are informed in real-time about the seat's occupancy.