Popular Reddit forum askReddit "is the place to ask and answer thought-provoking questions." One user asked for flight attendants to reveal whether or not they had ever caught any mile-high club member wannabes and what they did/would do about it. Many flight attendants answered with their experiences. Here's what they had to say:
Be discreet! A flight attendant said she's had people attempt to do their business in the galley where flight attendants sit! She's also had people who were rather loud moaners. Her advice - keep it in the bathrooms and BE QUIET! Turns out, those bathrooms aren't made to be soundproofed. Shocking.
You're better off on a flight that isn't full. One flight attendant observed two men engaging in hand play underneath the complimentary blankets. They were discreet and with the flight being close to empty, she let it slide. They did attempt to put their blankets back in the overhead bin to which she said "That's your blanket now." Follow up advice - never accept blankets that aren't in their original package.
Beware of turbulence and other passengers. Those doors to the bathroom can actually be opened from the outside and can also fly open if the turbulence is bad enough. Try to keep in mind that you may have to hold the door closed.
Use the bathroom, not the seats. A couple flight attendants said they've gone as far as calling federal martial's to meet at landings and banning passengers from flights.
Make it quick. One flight attendant said they had a couple waiting in the galley for 15 minutes as the woman tried to convince the man to meet her in the bathroom. Everyone knows what conversation you're having. Just make the decision at your seats and make it under 5/10 minutes.
If you have a moment, which you probably don't but oh well, try to wipe things down. Those bathrooms contain a lot of bodily fluids and germs. Not exactly the kind of surfaces you want the good china near.
Overall, the OP found that about 60% said that they let it slide as long as you're discreet, about 25% will break it up, and about 10% are going to go mall-cop on your nakey booty and get you in trouble.