Several improvements to optimize aircraft power plant and aircraft operations are disclosed, as well as methods of using these improvements to reduce fuel consumption, gas emission, noise, aircraft weight, maintenance costs, operating costs, aircraft incident and accidents, and improving aircraft performance. The improvements consist of a power plant fitted with a front propulsor, core engine, and aft propulsor. The fan of each propulsor is separated mechanically from the core engine. The front fan is separated mechanically from the aft fan. The aft fan is driven by free turbine that is supplied by exhaust gas of the core engine. If the core engine fails, both propulsors operate and provide thrust and reversed thrust when needed. If one propulsor fails, the other propulsor of the same power plant operates and provides thrust and reversed thrust.