This thesis deals with the topic of multi-connected multi-hub networks using the example of European airlines. Over the last decades the airline industry has undergone a period of drastic structural change. Especially mergers and capacity constraints at airports have left some European airlines with networks consisting of several hubs. Therefore this thesis on the one hand identifies and analyses those factors that are important for optimizing networks with multi-connected multiple hubs and on the other hand develops recommendations for airlines that have to deal with such a type of network. Hence, the first part of the paper focuses on factors that are important for managerial optimization of networks comparing the three network archetypes of point-to-point, single-hub and multi-hub. In addition, the second part tries to explore the interconnectedness of economies of density, scale and scope, the passengers' willingness to pay for direct connections or frequency, capacity constraints and cost advantages due to demand bundling for the different network types with an exemplary simulation based on the p-Hub Median model. 234 cases of parameter constellations were used as inputs for a linear target function maximizing airline returns. The multi-hub approach is often seen as inferior to a single-hub model due to losses in economies of density, scale and scope. However, an increased paid-for frequency of service together with the possibilities of exploiting several catchment areas, of improved compensation of demand fluctuations and of experiencing higher market power towards airports, may result in the advantageousness of the multi-hub system. The simulation shows accordingly that in the case of not too heavy losses of economies of density, scale and scope and a low difference of prices between direct and indirect routes, a high enough passenger willingness to pay for frequency may result in the multi-hub approach being the optimal solution. (author's abstract) / Series: Schriftenreihe des Instituts für Transportwirtschaft und Logistik - Verkehr