Initial studies of modular manufacturing processes have shown that this dominant design required a fundamentally novel organisational structure of the industries. The underlying hypothesis of technological determinism merits a deeper exploration. The first part of the present paper aims at presenting the logic of this argument while making a distinction between the technological and organisational aspects of modularity. Based on this we then attempt a study of the manner in which the transition to modularity takes place in the aircraft and automobile industries. Our main conclusion is that while it may be possible to posit a convergence between these two industries, the paths followed are still quite clearly opposed.