The HF Case is a process to systematically identify and treat HF issues and benefits during an ATM project throughout its lifecycle, from concept to decommissioning. The HF Case process is designed to be iterative and elements of it can be reapplied through each lifecycle phase as the project matures. It provides a comprehensive and integrated approach to ensure that the system can deliver the desired performance improvements and that the human performance contribution to these is optimised. The current HF Case is now in its third edition and has been validated and refined since its launch. This Edition 3 of the HF Case retains its emphasis as a simple, practical and effective approach to the consideration of Human Factors. The HF Case has five specific stages. Stages 1-4 provide the human factors integration process within a project. Stage 5 now provides integrated ongoing monitoring and validation throughout Stages 1-4 and provides a potential link to external processes such a Business, Safety Case or management process.