This report describes the challenges and experi- ences with the incremental re-engineering and migration of a 40 year old airport operations system. The undocumented COBOL legacy system has to be replaced within given con- straints such as limited downtime. A 3-step technical strategy is derived and successfully applied to the re-engineering task in this project. The incremental approach and resulting parallel operations of both systems are the most significant technical drivers for complexity in this environment. Furthermore, this report describes the process for planning, analyzing and designing a replacement system that is backed by strong user acceptance. The user interface design task of taking the system from VT100 to a web interface was a critical success factor, as well as live testing with actual production data and actual user interactions. Other aspects such as training and end user documentation are discussed.