Benefits of unitized structures for reducing cost and weight are well known and the applications are becoming more prevalent in aircraft structures. There are key design issues for primary unitized structures that remain to be solved. Some are damage tolerance in structures in which primary load paths are not physically separate, damage arrestment by other means, and damping of structures for noise and acoustic vibration reductions. We examine the benefits of unitized structures on a weight and cost basis and describe some of the methods used to determine business case for unitized structures. Cost analysis and weight assessment methods that are sensitive to the requirements of commercial aircraft structures are described. Some efforts to solve the damage tolerance issues presented by unitized structures are described and some methods to overcome these issues are presented. The cost and weight implications of these solutions are also presented. The rigorous life and damage tolerance requirements of commercial aircraft impose some different design philosophies between commercial and military applications. Today’s ability to model and simulate both the structural response and the damage progression in structures offers some interesting potential for new design solutions and some of these are presented along with a path toward future solutions. The ability to parametrically model unitized structures in detail and include crack growth analysis capabilities is expected to give us much more information with which to make informed decisions about what structures can be unitized and which cannot with today’s technologies. We expect that the push toward unitized structures in aircraft will continue and unique solutions will deliver damage tolerant designs and affordable solutions, but it will require the very best analytical and design tools available to achieve these solutions. Some of the needs for these tools are presented in light of the lessons learned from current experience.