HYENA (Hybrid Black-White-Modelling Estimation and Machine Learning Algorithms for  PNT Engines) is an ESA NAVISP project developing next generation Positioning, Navigation  and Timing (PNT) technologies that combine established estimation techniques with  advanced artificial intelligence and machine learning methods. The project investigates how  hybrid PNT engines can improve positioning performance, robustness and resilience in  challenging environments while maintaining the transparency, safety and trustworthiness  required for critical applications. HYENA will design, implement and validate novel hybrid  navigation architectures, including intelligent supervisory functions that manage and assess  the outputs of both conventional and AI-enabled algorithms. The resulting technologies will  be integrated into a real-time prototype and evaluated through representative field testing,  demonstrating their potential to deliver more accurate, reliable and resource-efficient  navigation solutions for future commercial and safety critical applications.