Since 2005, identical major projects have been planned in Germany and Austria simultaneously. Both Munich Franz-Josef-Strauss airport and the Vienna International Airport are planning to expand their airport infrastructure by building a third runway to increase the location-s capacity. While an almost smooth working process of planning could be initiated in Vienna, the proceedings in Munich were opposed by the majority of citizens, resulting in an early project failure through a public referendum. Significant differences in the nature and extent of participatory involvement, which are directly related to the divergent planning result, led to a different acceptance of the project in Munich and Vienna. Within the scope of this thesis, these planning differences are compared and examined. The breakdown of the laboratories, the expansion plans and conducted planning process in Munich and Vienna result in a gradual, in-depth-analysis of the process, which is discussed and assessed in an overall context of the legal and informal framework, planning culture and planning quality. This thesis points out the importance of a correct identification of problems, the appropriate planning approach and the active involvement of the public for planning projects and how this implementation can contribute to a positive project output in planning processes. It is based on a wide range of different methods, ranging from a partial evaluation to semi-structured interviews. These action and problem-solving approaches rely on the participatory integration method and are being presented based on a mediation process and displayed in a fictional scenario of a resuming process at Munich Airport. In addition, the transferability of previous results is tested on other regional and local planning levels. The objective of this thesis is to strengthen the positive aspects of "planning the (spatial)-Planning" and to achieve a sensitization in conflict-prone projects and their project developers.