Lift works opposite of weight. Thrust works opposite of drag. When the forces are balanced, a plane flies in a level direction. The plane goes up if the forces of lift and thrust are more than gravity and drag.

Is weight a thrust force?

Weight is the force directed downward from the center of mass of the airplane towards the center of the earth. It is proportional to the mass of the airplane times the strength of the gravitational field. Thrust is the force produced by the engine. It is directed forward along the axis of the engine.

What force opposes thrust?

Drag—a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.