The Flight Physics Concept Inventory (FliP-CoIn) is the first research-based conceptual assessment instrument for improving (fluid dynamics) learning and teaching. This work gives insights into why and how the FliP-CoIn was developed as well as how it is best used for improving conceptual learning. Further, this dissertation presents evidence for several dimensions of the FliP-CoIn’s validity and reliability. Finally, the author discusses key insights from the development process, the data analysis, and gives recommendations for future research. As such, this work is also written as a blueprint for future education researchers and instrument developers of other contexts. The FliP-CoIn’s context areas are flow, fluid dynamics and flight physics. The FliP-CoIn tests concepts of aerodynamic lift, aerodynamic drag, stall, center of mass, angle of attack and streamlines. The latest version and translations are available for educators at physport.org (or via flip-coin@uni-koeln.de).