The first sentence got me all psyched up to answer the question "What horizontal force do the engines generate in order to accelerate it ?".
But the actual question, in the second sentence, turned out to be a completely different one.
When the plane levels off and continues on at a constant altitude, it's not accelerating up or down, so the net vertical force on it is zero. The lift generated by the wings is exactly balancing the downward force of gravity on the airplane.
It is true that a physical change occurs when a material changes shape or size, but the composition of the material does not change. The correct answer is True.
