What are the four forces acting on an airplane in flight?

The four forces acting on an airplane in flight are lift, weight, thrust, and drag. Lift is the upward force that opposes the weight of the airplane, enabling it to rise off the ground and maintain altitude. Weight is the gravitational force that pulls the airplane down towards the Earth. Thrust is the forward force produced by the aircraft's engines, propelling it through the air. Drag is the resistance force that acts opposite to the direction of thrust, created by the friction of air molecules as they flow over the aircraft's surface.

Understanding these forces is crucial for pilots, as they must manage them to maintain control of the aircraft during various phases of flight. For instance, increasing thrust while managing drag and lift allows an aircraft to climb, whereas decreasing thrust while managing the weight helps in descending smoothly. This interplay of forces defines how an aircraft operates and responds to control inputs in different flight conditions.