 An example of a star that commonly causes this illusion is Sirius, which is the brightest star in the northern hemisphere and in winter appears over the entire continental United States at one to three fist-widths above the horizon.At dusk, the planet Venus can cause this illusion to occur and many pilots have mistaken it as lights coming from other aircraft 

False visual reference illusions may cause the pilot to orient the aircraft in relation to a false horizon; these illusions can be caused by flying over a banked cloud, night flying over featureless terrain with ground lights that are indistinguishable from a dark sky with stars, or night flying over a featureless terrain with a clearly defined pattern of ground lights and a dark, starless sky.This is when the brain perceives peripheral motion, without sufficient other cues, as applying to itself.