Les Hotesses Du Sexe - 1977

He is an old rich guy with a permanent erection who can't have an orgasm. (Not the usual problem with old guys, but also not unheard of...) The blonde has been hired by the doctor to get him off, but fails. Later in the film it turns out that he can come only when at 35000 feet—i.e. in the Sex Airline plane with the naked hostesses of the title of the film.

This is actually a portion in the middle of the movie. That said - love this individual clip due to the crazy music.

why did she shag the old dude?

Ah.. les petites Francaise 70'S