The context of product development (PD) in the aerospace sector is one of intense competitive pressure. To ensure the continued competitiveness of this industrial sector in Canada, enhancing the productivity of PD is an urgent necessity. Key tenets of lean include value, flow and continuous improvement. In the PD context, arguments have been made that lean is not minimizing cost, cycle time or waste, but maximizing value. The research reported in this thesis supports the overarching lean goal of continuously improving the value of information flow in PD by reducing span time. While lean has been used with much success in the manufacturing world, there is an absence of comprehensive models measuring the benefits of lean improvements in PD. The first major contribution to address is the development of a lean engineering multi-criteria performance model. In addition to the lean concept of 'one piece flow', notions of economic order and production quantity are used in manufacturing to address the objective of flow improvement, and the related objective of inventory management. Equivalent economic design quantity concepts to address inventory of intellectual work in progress are lacking in PD. Thus, the second contribution of this work is the development of both analytical and experimental models to help ascertain the existence of optimal PD job size. The final contribution of this thesis is the development of lean decision-making models to enable optimal allocation of PD resources, supporting the lean objective ofimproving the value ofinformation flow.