This project follows the development of airport transit zones during the second half of the 20th century. Sometimes thought of as ahistorical “non-places,” the transit areas of international airports, from the perspective of this research project, are historical sites brimmed with social context and constantly reshaped by local, national, and global dynamics. Alongside the rapidly growing international air traffic, they evolved from simple waiting rooms and turned into multifunctional border zones located on sovereign territory in the interior of a country and yet having extra-territorial features. The project shows how, through their spatial ambivalence, transit zones came to fulfill a key function in mediating between the liberal movement of people on the one hand and states’ desire to control their territory on the other. “History in limbo” is thus an assessment of both, “doing border” and “undoing border” in times of globalizing passenger traffic. Drawing on perspectives from global history and mobility studies, it reaches beyond aviation history and puts the history of transit zones in the context of an increasing transnational management of air mobility since the late 1940s. The project consists of two sub-projects. (1) The habilitation thesis focuses on Frankfurt, Germany’s busiest transit hub. Based on research in local, state, and international archives, it presents a close-up view on the actors, strategies, and interactions involved in the making of the transit zone (e.g. border police, international organizations, retailers, passengers). This approach promises insights into changing strategies of mobility control as well as the small-scale dynamics through which they were implemented or challenged on the ground. In a more general sense, the study aims at exploring the Bonn (and later Berlin) Republic’s historical engagement with globalization processes by shedding light on its most frequented “border with the world” and the ways this border was made, perceived, and contested. (2) The second book project embarks on a wider global history of airports and their role in migration/asylum history. Comparing and connecting different cases from North America, Europe, and Asia, the study asks whether we can identify the emergence of a new transnational migration regime in the 20th century that was specifically targeting airports and the challenge they posed to territorial orders. The study also examines the specific conditions of migrant agency at airports revealing both restrictions and opportunities the refugees encountered on site.