Airplane
The mile-high club gives you a clue of how long people have been having sex in airplanes. Nowadays, commercial flights travel at an altitude 5 miles high. There are lot of ways to do it in a plane. It just requires several things including timing, a relatively empty cabin or access to the restroom, maybe a blanket if you are in your seat, and if possible, a wink of permission from the flight attendants. Yes, they know.
