Product development projects, especially in the aerospace industry, still suffer from significant cost and schedule overruns. Many researchers and scientists focused first on process and tools to shorten the time and reduce the cost of new product development projects. The results were far from resolving this issue. Thus, the focus was reoriented toward enhancing the accuracy of estimates. Thereby, a large number of research papers were published regarding effort and time estimation in new product development. Most of them are modeling based on the use of some specific drivers for estimation matter. However, to the best of our knowledge, there are no rules or frameworks about which drivers are relevant to use and which are not. This paper proposes a new and original framework that characterizes and organizes effort and time drivers in aerospace product development. The aim is to identify and support the understanding of most relevant drivers for aerospace product development effort and time. The framework was developed based on an extensive literature review and a postmortem analysis of cost and time overruns of a significant product development program in the aerospace industry. The final list of the frameworks’ drivers was validated and refined using a survey. Results suggested that, beside risks and uncertainty, technologies maturity, degree of change in design, ambiguity of requirements, functional decompositions, severity of standards, process overlapping and variety of key stakeholders drive effort and time as complexity drivers while processes maturity, experience with technology, risk management, change management, level of trust in suppliers and team skills drive effort and time as proficiency drivers.