Shorter development cycles, increasing complexity due to the interaction of hardware and software and the simultaneous pressure to innovate and reduce costs lead to products being launched early that have not yet been sufficiently validated and tested. The prototyping phase is crucial to ensure maturity as a preliminary stage to series production. Although this validation is critical to ensure the maturity of the product or technology to avoid recalls, previous research has focused on exploring the phenomenon of prototyping in general. To fill this gap, we use the standardized framework of technology readiness levels and develop prototyping readiness levels that allow for a graded assessment of maturity.Our empirical study is based on the unique case of the Boeing 737 Max 8 and a research project to develop an automated prototyping hub. Our findings show how mismanagement of prototypes and inadequate technology readiness level (TRL) assessment can lead to serious safety issues. Based on these findings, we introduce prototyping readiness levels that complement the idea of TRLs to reduce and eliminate bottlenecks and errors in the early stages of the development process.