First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is cruising, and secondly, the thrust from the propulsion system must exceed the drag of the airplane for the airplane to accelerate.
The thrust from the propulsion system must balance the drag of the airplane. This is first. The airplane is cruising. First the thrust from the propulsion system must exceed the drag of the airplane for the airplane to accelerate. This is secondly.