The inaccuracies in the modern theory of air-jet engines are considered associated with the erroneous thermodynamic cycle of turbojet engines in the P-V, T-S coordinates, with the erroneous formula of thrust, with the erroneous formula of flight (traction) efficiency of turbojet engines, with a misguided theorem about the lift force of the blown profile, with an erroneous understanding of the Euler equation, which leads to a complete discrepancy between theoretical and experimental data, to inaccurate design of air-jet engines that reduce their gas-dynamic stability during take-off, flight, landing, which leads to lower flight safety, environmental and technical and economic indicators of air-jet engines, to the impossibility to develop the proper directions of technical progress in the field of aircraft engine construction. The monograph addresses the development and derivation of the fundamental basis of a unified theory of engines on continuous streams associated with the development of a fundamentally new thermodynamic cycle of turbojet engines in the P-V, T-S coordinates, with the derivation of fundamentally new formulas of thrust, flight (traction) efficiency of any engines on continuous streams, including various types of TRD, TRDD, TRDF, RD, etc., with the derivation of a fundamentally new theorem about the lift force of the blown profile, with all the fundamental foundations of a unified theory of engines on continuous streams fully corresponding to all experimental data from the modern theory of air-jet engines. A description is given of the real zone of inhibited flow, which is generated in front of the air intake of any WFD, and based on kinematic analysis, a fundamentally new interpretation of the theoretical and physical fundamentals of generating unstable operation (surge) of jet engines during takeoff, flight, landing is given. A fundamentally new approach to the determination of energy flows consumed by the engine along the first and second turbofan engine circuits is given. A description is given of several areas of technical progress in the theory and design of spinning propellers, in the theory and design of turbojet engines, associated not only with the issue of increasing propulsion thrust, but also with increasing their gas-dynamic stability during take-off, flight, landing, which significantly increases flight safety improves. environmental and technical and economic indicators of the engine.