The planning process in Engineer-To-Order (ETO) projects is challenging due to: global network of participants within a project, dynamic iterations on design and engineering activities as well as the need for completing activities in a concurrent manner that shorten the delivery time. Moreover, managerial decisions on what and where to outsource disturbs the planning process due to lack of integration between different working methodologies or systems. In this article, we present some of the challenges faced during the planning process and connect them to the project execution strategy applied by ETO companies when managing their projects.