In this paper, we try to propose a regional planning approach for reducing the damage by airplane accident. We first survey the concept of region in the ICAO Airport Work Manual and some airport emergency plans in Japan. The region can be defined as such areas as the stricken area, the possibility stricken area and the two kind of backup area (surrounding functional area and the surrounding administrative area). However they have partitioned either spatially or juristically, it needs to develop the method for evaluating and partitioning the backup area. Secondly we apply the Related Tree Method to evaluate the regional potential concerned with rescue activity in the backup area. As the result of the case study, the difference in regional potential among surrounding areas has clarified. As for the airport located at offshore, the potential of the backup area should be re-evaluated by the criteria different from those for the ordinary airports. Thus the characteristics of airport itself and its surrounding area should be taken into account for rescue activity planning as well as commercial and development ones.