Contrast with Background
Your ability to detect and recognize aircraft improves with increased contrast between the
aircraft and the background (Figure 3). A black object against a white background can be
visible to you at a great distance, while the same object viewed against a dark background
may be visible only at a short distance. Your ability to detect and recognize an aircraft
will decrease when the background is vegetation or bare mountain slopes, and will
increase when the background is overcast sky (as opposed to the bright blue of sunny
days). Smoke trails produced by jet aircraft are valuable aids to you in detecting at long
ranges under conditions of poor contrast. Motion against the background also improves
detection ability. Conversely, aircraft hovering or moving at low speeds are difficult to
detect.
Visibility Conditions
An aircraft may be visible to you at a long distance in a clear atmosphere, while dust, fog,
haze, rain, or snow may reduce your detection range to a short or, in extreme cases, zero
distance (Figure 4).
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