<P> The mile - high club is slang for the people who have had sexual intercourse on board an aircraft . </P> <P> An alleged explanation for the act is the supposed vibration of the plane, which may lead to sexual arousal among men . Some say they have fantasies about pilots or flight attendants, or a fetish about planes themselves . For others, the appeal of joining the mile - high club is the thrill of doing something taboo and the thrill of the risk of being discovered . </P> <P> An early reference to the concept is found in the betting book for Brooks's, a London gentlemen's club . The 1785 entry (only two years after the first successful balloon ascent by Étienne Montgolfier) reads: "Ld . Cholmondeley has given two guineas to Ld . Derby, to receive 500 Gs whenever his lordship has sex with a woman in a balloon one thousand yards from the Earth ." (However, there is no further indication that the bet was paid, or even how they would check it if it was claimed .) </P>

What is the boat version of the mile high club