An autothrottle (automatic throttle, also known as autothrust, A/T) is a system that allows a pilot to control the power setting of an aircraft's engines by specifying a desired flight characteristic, rather than manually controlling the fuel flow. The autothrottle can greatly reduce the pilots' work load and help conserve fuel and extend engine life by metering the precise amount of fuel required to attain a specific target indicated air speed, or the assigned power for different phases of flight. A/T and AFDS (Auto Flight Director Systems) can work together to fulfill the whole flight plan.