This study provides insights into the legitimation process of emerging ecosystems and strengthens the conceptual link between entrepreneurial ecosystems and economic geography. It examines existing theoretical frameworks on legitimation strategies in emerging entrepreneurial ecosystems by inquiring into advanced air mobility (AAM), an area in which innovation faces exceptionally high legitimation challenges. The initial integration of drones for logistics and air taxis for passenger transport is surrounded by ambiguous future visions that range from high expectations to concerns about developing a mobility form that is neither sustainable nor socially acceptable and affordable. Empirically, this article offers an analytical understanding of the collective legitimation strategies within the emerging AAM ecosystem in Hamburg, Germany. For this, we used multiple qualitative methods and data sources: (1) a contextualizing network analysis, (2) semi-structured interviews with 22 representatives of tech and policy development, and (3) participatory observation from applied research projects. Based on the empirical material, we find that the current conceptual debate underestimates the public sector's role in ecosystem emergence and legitimation. As AAM depends on fundamental regulatory change, authorities and state-owned companies in the aviation sector have a decisive influence on the emergence of the ecosystem. Furthermore, our findings highlight how global discourses shape local practices and expectations. By combining cross-sectoral knowledge, entrepreneurs and policymakers aim to identify feasible use cases for their place-specific context. Nevertheless, the lack of a collective identity within the ecosystem, which comes largely from the uncertainties of AAM, poses numerous challenges for ecosystem participants addressing their liability of newness.