Landing airplanes, detecting traffic, and dark focus

Misjudgments of position in flight and failures to detect other airborne traffic are casualties of the eternal tug-of-war between visible texture and the pilot's dark focus. The eye is lazy and resists the pull of a distant stimulus, preferring to rest at a relatively short focal distance, as it does in the dark or when looking at the sky. Judgments of apparent size are highly correlated with visual accommodation distance, and the difficulty of detecting airplanes on stationary collision courses is greatly aggravated when focus is trapped by structure close to the eyes. Subject, cockpit design, task, and environment variables all interact to determine what we think we see.