Principles of Flight - Four Forces of Flight (2)

Speaking of four forces, you may notice from the below diagram that they are not lie on the same point. 

In fact, it is designed in most conventional aircraft that the center of pressure (where Lift acts upon) is behind the center of gravity (where Weight acts upon).

Since the Weight is ahead of Lift, the aircraft has a tendency to pitch down. To balance the aircraft, engineers intentionally place Drag above Thrust, leading to a pitch up tendency.

Besides, the presence of the tail-plane (horizontal stabilizer) also helps counteract the pitch down tendency making the aircraft more stable.