Keep Your Pants On
With far less instrumentation, early pilots had to rely on their own senses a lot more to fly. Their rear end had some of the most direct contact with the plane, from which they could feel engine vibration, angle, and other input. This is why flying intuitively with little or no input from instruments and radios came to be known as “flying by the seat of your pants.”
The association with the person who “wears the pants in the family” (or trousers of you’re British) being the family decision-maker it is simply based on the fact that only men historically wore pants and also traditionally had that role.
That garment likely covering your legs is named for a creepy old man common in European theater a few centuries back. Crafty, greedy “Pantalone,” whose schemes often failed and led to his humiliation, was a stock character in plays from the 16th-18th centuries. Early on, he typically wore breeches and red stockings, but in later years wore long trousers. When similarly-styled trousers caught on outside the theater, they were called “Pantaloons” in England, which eventually got shortened to just “pants, ” which is part of “underpants” and “panties.”