The document discusses the performance management of functional airspace blocks (FABs) in air traffic control systems, highlighting the economic and organizational challenges posed by hybridization. It emphasizes the importance of evaluating FAB performance through appropriate metrics, such as cost-benefit analysis and Generalized Latent Linear and Mixed Modeling (GLLAMM), to address inconsistencies in data. The study suggests significant predictors for FAB performance, including safety management, cost of delays, and volume of controlled airspace, while also identifying areas for future research.