Mass customization is an approach that provides methodologies for the development of customized products while still profiting from the benefits of mass production such as economies of scale. Today, mass customization approaches have found their way into different industries such as clothes and furniture but also, to some extent and named differently, into more complex products like cars. Products like busses, trains, or aircrafts are not particularly known for applying similar approaches. They deal with complex systems that are highly regulated by legal requirements and thus seem to be restricted with respect to their possible degree of customization. This paper presents results from a study that was conducted in order to analyze applied practices in these industries. One of the goals of the study was to detect limitations of today’s mass customization approaches that prevent an easy applicability. Configuration and customization approaches in the airplane cabin design, in the bus and in the train industry were investigated and compared. Finally, shortcomings in the applied practices and in the supporting solutions were identified and suggestions for improvements were formulated.