Abstract: A mathematical model of communication region should be developed for realizing normal communication of two aircraft in flight. Based on the air-to-ground wireless datalink communication, the wireless datalink communication area between two aircraft was analyzed by considering the factors such as transmitters, receivers, send and receive antennas in communication datalink, transmission space and earth curvature, vehicle attitude angle and space positional relationship of aircrafts from implementing the normal communication conditions. A mathematical model of wireless datalink communication area between two aircraft was developed, including antennas, flight altitude, space positional relationship of two aircraft, communication area models and so on. The model has been successfully applied to a particular model; it provides a reference for analyzing air-to-ground wireless transmission system communication area based on the wireless datalink communication, and supplies for the spacecraft, satellite and other air-to-air, air-to-ground wireless data communications systems.