"These phantoms speak with human voices — friendly, vapor- like shapes, without substance, able to vanish or appear at will, to pass in and out through the walls of the fuselage as though no walls were there. At times, voices come out of the air itself, clear yet far away, traveling through distances that can't be measured by the scale of human miles; familiar voices, conversing and advising on my flight, discussing problems of my navigation, reassuring me, giving me messages of importance unattainable in ordinary life."