Flying an airplane is a perceptually learned process in terms of the pilot understanding invariants for the ecological control of the aircraft (Benson, 1999; Lintern, 2000). Salient visual cues used by a pilot are above sensory threshold and provide perceptual information for accurate aircraft control. Therefore, for a visual cue to be perceptually effective, it must convey information to the pilot. If an aircraft control input is made that alters the spatial position of the aircraft, cues within the visual scene need to reflect that change. Thus, the best visual cues for a pilot to perceive are those that are sensitive to even the slightest aircraft positional change. A visual cue that does not change given gross aircraft control input is probably not an effective cue (Lintern). However, some visual cues, by remaining constant, provide information to the pilot; these are called invariants.