The thesis discusses the spatial-economic and institutional positions as well as institutional learning in the development process of airports as cityports in city-regions. Cityports are therein defined as urban centres where economic activities and infrastructure are at crossroads and are the gateways to the city-region. Amongst other new urban centres as edge cities and new business centres, airports are increasingly becoming these gateways to the polycentric city-regions, as well as a transportation nodes and places to stay. The locations contribute to the increasing importance of the city-region’s global competitiveness. The particular focus is on the development of airports as cityports, with case study airports of Schiphol, Frankfurt, Haneda and Narita. Schiphol makes full use its potential near the airports and develops towards a monocentric airport city, which generates congestion. Frankfurt applies the potential of the hub as well, where possible congestion of the airport is limited by its location in Frankfurt’s forests and an extensive regional light rail system. It develops as a polycentric airport city in the Rhein-Main city-region. In the case of Tokyo’s airports Haneda and Narita, there is less coherence between economic potential and development towards a cityport. Urban development of in particular warehouses in remote Narita is limited and scattered over the region, referred to as sprawled aerotropolis. Although Haneda is mainly a domestic airport, it is still Asia’s largest. However, little urban development is found at this isolated airport island, with few economic spin-offs for Tokyo and Kawasaki. In addition, also planned airport city developments in coastal towns near the new airport islands of Kansai and Nagoya shows little success in the development of cityports. As spatial-economic reasons are not sufficient for understanding differences in cityport development, an actor-oriented institutional analysis provides insight. Various socio-cultural, financial, economic, governance and legal rules of the game either hamper or support the airport area development process. In particular consensus and pragmatism, a regional patchwork quilt of coordinating agencies with limited jurisdiction, unclear role differentiation between control and development for both ministries and airport, contribute to the semi-contested silent growth coalition with a short-term focus in the case of Schiphol. In Frankfurt, trade-offs created by politicisation of planning, local specialisation, the light rail network and decentralised planning contribute to the contested open growth coalition focussed on the medium term. High land prices, infrastructure-related economic development, citizens’ opposition, and centralisation of planning leads to a conflict-avoiding growth coalition with expensive solutions for the long-term in Japan. Although it is difficult to copy successful institutions that contribute to the development of the airport as a cityport to other cases, the comparative analysis offers a mirror as well as future perspectives for spatial-economic development and reshaping institutional arrangements.