What do thrust and power required primarily depend on?

Thrust and power required are primarily influenced by drag because as an aircraft moves through the air, it encounters resistance known as drag. This is a crucial aerodynamic force that must be overcome for the aircraft to maintain its flight speed.

To sustain level flight, the thrust produced by the aircraft's engines must be equal to the drag force acting on it. If drag increases, for example, due to increased air density at lower altitudes or changes in configuration (like extending flaps), then the engines must produce more thrust to counteract that drag. Consequently, the power required by the engines will also increase to provide the necessary thrust.

While weight, altitude, and temperature can have secondary effects on the performance of the aircraft, such as altering lift requirements or engine efficiency, drag is the primary force that directly dictates the amount of thrust and power an aircraft needs during a given flight condition. Thus, understanding the role of drag is essential for predicting the operational performance of the aircraft in various flight scenarios.