Figure 6-3. PPC attitude is based on relative positions of the aircraft on the natural horizon.  Figure 6-4. Nose reference for straight-and-level flight.  Straight-and-level flight is flight in which a constant  heading and altitude are maintained. It is accomplished  by making immediate and measured corrections for  deviations in direction and altitude from unintentional  slight turns, descents, and climbs. Level flight, at first,  is a matter of consciously fixing the relationship of  the position of some portion of the PPC, used as a  reference point, with the horizon. In establishing the  reference points, place the PPC in the desired posi - tion and select a reference point. No two pilots see  this relationship exactly the same. The references will  depend on where the pilot is sitting, the pilot’s height  (whether short or tall), and the pilot’s manner of sit - ting. It is, therefore, important that during the fixing  of this relationship, you sit in a normal manner; other - wise the points will not be the same when the normal  position is resumed. In learning to control the aircraft in level flight, it is  important to use only slight control movements, just  enough to produce the desired result. Pilots need to  associate the apparent movement of the references  with the forces which produce it. In this way, you can  develop the ability to regulate the change desired in  the aircraft’s attitude by the amount and direction of  forces applied to the controls. The pitch attitude for level flight (constant altitude) is  usually obtained by selecting some portion of the air - craft’s nose as a reference point, and then keeping that  point in a fixed position relative to the horizon. [Figure  6-4] Using the principles of attitude flying, that posi - tion should be cross-checked occasionally against the  altimeter (if so equipped) to determine whether or not  the pitch attitude is correct. If altitude is being gained  or lost, the pitch attitude should be readjusted in rela - tion to the horizon and then the altimeter rechecked to  determine if altitude is now being maintained. The ap - plication of increasing and decreasing throttle is used  to control this attitude. In all normal maneuvers, the term “increase the pitch  attitude” implies raising the nose in relation to the ho - rizon (by increasing power); the term “decreasing the  pitch attitude” means lowering the nose (by decreas - 6-4