There are four major forces acting on an aircraft in flight. Lift is the upward force countering gravity. The aircraft must produce enough lift to fly. Thrust is the push or pull forward that allows the aircraft to move. Drag is a slowing force.
Drag always acts in a direction opposite thrust.
Drag Drag is associated with lift. It is caused by any aircraft surface that deflects or interferes with the smooth airflow around the airplane. Drag acts in opposition to the direction of flight and limits the forward speed of the airplane. Decreasing drag makes things go faster. Increasing drag makes things slow down.