The main object of this paper is to study the role of buffer in the process of airspace planning, so as to obtain an efficient and optimal air traffic system configuration. Specifically, this paper proposes a system modeling method to describe the nonlinear air traffic flow dynamics. The purpose is to find an optimal allocation scheme for each flight plan and define the operation process of each sub-segment. First, the model of an air traffic system with buffers is built, and it can switch between different configurations. In each configuration, the system model is described by specific parameter sets, and the configuration variation allows us to change the structure of the air traffic system. Then, we discuss some performance measures of the air traffic system and indicate how they can be applied to obtain optimal buffer allocations. The main objective of this paper is to investigate the performance of terminal control area.