The flexible use of airspace and its practice are the key components of next generation air transportation system and the important technical support of reconstructing the national airspace in Europe, Japan and other countries. On the basis of overview and comprehensive cognition of the generation, implementation and aims of flexible use of airspace, the design methods of sector’s boundary changes were evaluated. Then, from the perspective of “sector-closed”, the effect on sector boundary changes was evaluated, and the time alternative mechanism in flexible use of airspace was revealed. The research shows that “Algorithm+Manual Dynamic Boundary Change” can be a method for better distribution and balancing the unbalanced traffic demand across regions, which will also promote the airspace development and capacity release. The flexible use of airspace based on ICTs realizes the replacement of the factor of space by the factor of time, which enhances the flexibility of airspace configuration and the changing of air routes to the maximun extent. The methods and applications of flexible use of airspace will be not only beneficial to establishing the whole national airspace system and utilization, but also to promoting geography research on airspace resources development and the studies on connection between air and land.