Forces on an aircraft are essential for understanding how it flies. The four main forces are lift, weight, thrust, and drag. Lift is the upward force generated by the wings, allowing the aircraft to rise. Weight is the downward force due to gravity, pulling the aircraft toward the Earth. Thrust is the forward force produced by engines, propelling the aircraft through the air. Drag is the resistance force that opposes thrust, caused by air friction. Balancing these forces is crucial for stable flight, enabling the aircraft to climb, descend, and maneuver effectively.