The principal objective of this article is 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 definition and the production of systems or sub-assemblies. A particular characteristic of the hub firm is the way it develops linked organisational and geographical proximities which this article analyses in detail. In particular, such firms demonstrate the capacity to establish different types of organisational proximity according to whether they are coordinating with the architect-integrator or with subcontractors , proximities sometimes reinforced by a temporary geographical proximity. When hub firms coordinate with industrial or scientific partners which help them 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.