This report consists primarily of four chapters that each investigate problems that in one way or another concern the so called negative externalities of Stockholm- Arlanda Airport, i.e. the societal costs that arise as a consequence of the airport's activity. The reason that the problems are difficult to resolve, and in some cases more or less infected, is that different people have fundamentally different views concerning how the world ought to be. Even if they, in some cases, agree on the facts, it is difficult to reach a consensus with regard to the normative aspects of the problems. The overarching purpose of this report is to formulate, delimit and represent the problems and to provide a conceptual apparatus suited for discussing and possibly solving them. Given this purpose, philosophical ethics and decision theory are the knowledge domains the most suited to form the basis of an in-depth treatment of the issues involved. In addition, insights into aviation at Arlanda are necessary. The Swedish Defence Research Agency, FOI, is arguably one of the few institutions in Sweden that combines these two areas of expertise. As a result, FOI has undertaken this investigation at the request of LFV (later transformed into Swedavia AB). The work was initiated in November 2009 and finalized in February 2010. The results are primarily intended for use in Swedavia's coming application for a new environmental permit for Stockholm-Arlanda Airport, but also to provide general guidance when it comes to organizational decision making related to the topics treated.