In this book, the complete theory systems and frameworks of aircraft testability and fault prognosis techniques are established.The common testability design analysis, fault diagnosis and prognosis methods of aircraft are introduced comprehensively. The objects of the book are to stand out the characteristics of aviation, to pursue comprehensive and detailed content, and to emphasize the combination of theory and application. In the aspect of theory, the advanced theories and techniques including signal analysis, multisignal modeling, test strategy optimization, sensor placement and sensing strategies,fault diagnosis methods, fault prognosis techniques and so on, which are involved in aircraft testability and fault prognosis, are all introduced in detail. In this book, aircraft testability and fault prognosis techniques include: testability modeling and analysis for aircraft system fault diagnosis and prognosis, vibration monitoring and fault diagnosis for aeroengine, trend analysis of aeroengine, and nondestructive testing of aircraft structure. In this book, many diagnosis cases are arranged in order to make theory to combine practice. The book can be acted as the teaching material for senior aircraft maintenance majors, and reference book for postgraduate and technician of this major and related majors.