Actually, Conrad is aware that he is not thinking full-blown thoughts, but highlights, like the trailers at his local cinema complex; these thoughts are presenting themselves to him in a chaotic pageant. It is in the nature of air travel with its barely suppressed claustrophobia and its sexual speculation and dulled sense of movement that thoughts seem to be provoked to go on the exuberant march. (You can only think about thoughts, or consciousness, in metaphors.)