urpose - The aeronautical industry is a perfect example of a complex product industry characterized by a hierarchically-organized supply chain. The authors can identify four types of supplier interfaces: interactive, translation, specified and standardized ones. The purpose of this paper is to understand the factors explaining the diversification of these relationships between aircraft manufacturers and their suppliers, through the example of Airbus suppliers. Design/methodology/approach - Network analysis (to define the complexity level of aircraft components), data analysis (to characterize the diversity of aircraft suppliers) and a logit model were combined in order to link the supplier interfaces to the complexity of components and to the suppliers' characteristics. Findings - It is shown that the earlier a supplier is involved in the development process, the more responsibility is delegated to him and the more intertwined its relationship is with the prime contractor. Also, it is shown that component complexity plays a major role in a supplier's involvement during the integral design and face-to-face interactions matter greatly during the co-design phases of the products. Research limitations/implications - The research has rather a static perspective covering all the inter-firm relations within Airbus programs at once. By using the same databases, one could look into the evolution of supplier interfaces within the aeronautical supply chain. A dynamic view would provide some evidence regarding the recent restructuring of the supply chain. Originality/value - The originality of the paper comes from the methodology and the use of original data allowing to test in the same analysis the role of the component complexity and the characterization of the suppliers on the form of relationship between the manufacturer and its principal suppliers.