The development of smart space and its technical system has expanded the traditional cognition of physical space-time domain. Time and space are essentially integrated and continuous, and they overlap with the information space. The organic integration of the space-time domain with the information space can enable information technology to further its control over the physical space. To address the problems of and needs for airspace management, we propose a digital airspace system and construct a four-dimensional air traffic space-time framework in a physical–information fusion space, realizing the digital reconstruction of airspace management. Furthermore, a set of control theories and methods for digital airspace management is developed. Large-scale computing technology is utilized for analyzing the operating structure and control mode of the digital airspace system, also for decision making and use configuration, thereby laying a theoretical foundation for the coordination of airspace, air traffic flow, and air traffic control. Moreover, we propose suggestions for the development of the digital airspace system in China. A national plan for airspace system development should be formulated to coordinate the civil and military air traffic infrastructure construction. The scientific and technological innovation mechanism should be improved to build an innovation platform for the national airspace system. The overall coordination and resource integration of air traffic control innovation should be strengthened to improve the research and innovation plan for airspace management.