Human Factors interventions compete for resources in an airline maintenance environment. Senior managers ask for measures to show how human factors interventions can affect the “bottom line”. They want to know the return on investment in human factors. This paper looks at research, in progress, that has the goal of reducing installation errors in heavy aircraft maintenance. Working with two large carriers and a large repair station, the project has established the goal of a 50 percent reduction in selected error categories. The paper summarizes the rationale for the research and the current state of the research project. We describe the data collection methods, the plans to develop interventions, and the challenges expected as we quantify the return on investment.