Which force must be overcome for an aircraft to ascend?

For an aircraft to ascend, it must generate enough lift to overcome the weight of the aircraft. Weight is the force due to gravity acting on the aircraft, pulling it downward. To achieve a climb, the lift produced by the wings must exceed this weight. When thrust provided by the engines propels the aircraft forward, the airflow over the wings creates lift. However, if the lift does not overcome the weight, the aircraft will not ascend, and it may even descend instead.

While drag, which opposes motion through the air, and thrust, which propels the aircraft forward, are both important in the overall dynamics of flight, they do not directly relate to the ability to ascend. Lift is essential for counteracting weight, making it the critical force in the context of ascent. Once lift exceeds weight, the aircraft can then climb effectively into the sky.