National Geographic : 1918 Jan
Photograph by Edwin Levick OUT OF THE STORM The most dreaded Nemesis of the cadet aviator is a 'dead hole" in the air-an area of extreme low pressure caused byascending and descend ing currents. When a plane reaches one of these spots it drops like a plummet. Dead holes aboundinsummer-time up toaheight of1,ooo feet, and on extremely hot afternoons they have been encountered at elevations of a mile. They are much less numerous onwinter days, and arepracti cally non-existent at night; so that night flying is safest, so far as "holes" are concerned.