The principal objective of this paper was to offer an approach to the notion of hub firms using concepts from the economy of proximity. It shows that the specificity of the hub firm lies in its ability to combine technical and relational skills, allowing early involvement with, for example, an aircraft manufacturer in order to take part in the design and production of systems or sub-assemblies. A particular characteristic of the hub firm is the way it develops linked organizational and geographical proximities which this article analyses in detail. In particular, such firms demonstrate the capacity to establish different types of organizational proximity based on whether they are co-ordinating with the architect-integrators or with sub-contractors, proximities sometimes reinforced by a temporary geographical proximity. When hub firms co-ordinate with industrial or scientific partners, which help them to conceive and master particular sets of skills, they often forge links based on geographical proximity in order to develop the innovations necessary for the acquisition and master of these in-house skills. These theoretical arguments are then tested in the cases of the hub firms Thales Aerospace and Liebherr Aerospace in the Toulouse aeronautical complex.