The ambition of our engineering school is to train competitive engineers who are able to manage complex projects in fast-changing environments. To this end, we have developed a project based course, controlled by teachers (Steering Committee), where students are confronted with a practical long term assignment which includes unexpected events. Over the six years of experience gained in running the course, the important question of leadership has emerged, even though it was not an a priori explicit objective of the course. In a large group, if responsibilities can be relatively easily identified and assigned, the group dynamic often relies on the presence of one or several leaders. The Steering Committee puts pressure on the student groups to highlight the capacities of the leader(s) and those around him/her/them. The bounds of the exercise are established by the natural peer-to-peer relationships between fellow students in each year group. Even if the project does not run well, even if the project leader makes mistakes, leadership skills are understood by the whole group and students still acquire skills. We debrief with the students in order to relativize the success of their production in relation to the organization of the group. Different leadership situations are analysed and discussed in this paper.