The management of transport infrastructures has undergone major reforms in recent decades, including privatization, de-bureaucratization, and regulation. One important but often neglected issue in the management of large transport facilities is the joint governance of ports and airports, a phenomenon that is relatively frequent in the US but not in either Europe or Asia. To examine the factors explaining the joint management of ports and airports we undertake a multivariate empirical analysis in a sample of US metropolitan areas. We find that joint management of these infrastructures is more likely in the smallest and largest cities, and less likely in medium-sized cities. It is also more likely in areas with ports and airports of similar magnitude, because there is room for exploiting scope economies. Finally, we find that joint management is less likely when there is large-scale involvement of private firms in port activities, as in the landlord model.