Researchers from the Politecnico di Torino working in different fields and a start-up company from the internal incubator decided to join together in a collective project to produce an innovative light aircraft that would utilize hydrogen as fuel. Several decisions have had to be made, above all in relation to the hydrogen fuel cells that have to be used (dimensions, number, supplier,...) and to the electric propulsion engine that has to be combined with the cells as there was no engine on the market with the adequate characteristics. The consequences of these decisions (and of others, in relation to the electronic devices and the automatic control systems), in terms of times, costs and risks, have had to be analysed in the project context, where units with different expertise and language were involved. The paper proposes a methodological approach to identify and face uncertainties and complexities pertaining to this multiunit project through a shared vision of the problems and a structured and evolving problem formulation that has been developed to support communication, coordination and decision-making. It explains how some tools have been integrated in this application and used to elaborate and represent alternative decisions, to collectively evaluate and choose and to create a communication space for the project.