It's a fun and fascinating site. My experiences don't add much (guess I was a little shy to get into many good situations) but there was this one time a couple of years ago when my lady and I got venturesome...
My Lady and I were headed off to Costa Rica for a long weekend, on an 11:55 red-eye flight from LAX. She was sitting in an aisle seat, I was in the middle (B) seat, of the six-wide Boeing. We sat watching the rather lame in-flight movie and after a while I started counting cliche's to her. She shushed me, and unfolded the blankets she had picked up as we boarded. She spread them out over us, and finished covering up with our jackets, then settled back to watch. When I figured we had seen a new record set for cliche's in one movie, I started teasing her by, every time the leading man appeared, sliding my hand over her upper thighs. When leading man and leading lady started getting close, I started massaging her pussy through her jeans. For a while she brushed me away, looking around to see who might be looking. Finally, the movie reached its climax, and so did she. But she held it in, and only gave a silent little shiver, then pushed my hand away and settled it firmly in my own lap.
The movie ended a little after 2:00AM, people stirred around a bit, then it got quiet. Flight Attendants were chatting in the forward galley, and my lady looked around again, then quietly folded up the blanket and jacket, and unbuckled. She giggled quietly, then stood up and motioned for me to follow. OK, whatever, I figured. Maybe she wanted to change seats. But she started toward the back of the airplane, still motioning for me to come along. I could see where a third attendant was sitting reading in the aft galley, but Lady pushed open a lavatory door and motioned me inside. Then she slipped in with me and slid the bolt on the door.
'I always wanted to try this, didn't you?' she asked. She pressed in close and started giving me deep, intense kisses. 'It's the Mile-High Club, you know. Very exclusive.'
Also, a very small clubroom I realised. We're not really big people, like you see these days, but positioned the way we were, me against the forward wall, her against the tiny washbasin shelf, we could barely move. I couldn't imagine trying to do it on the commode, and didn't fancy dropping our jeans on the floor. (besides, I wasn't sure we could reach them if we did.) So I went for the next best, unhooking her bra and playing with her breasts and nipples, then undid her jeans and slipped my hand into her panties. She was ready, and this time she didn't have to hold anything back, with the lavatory walls surrounding us, and the higher noise level back there. She was gasping and interrupting our kisses to moan 'Ohhh', every now and then, and then I felt her start to cum. It was magnificent. She shook all over. She shook the whole lavatory. She shook the whole airplane. Then I realized she had finished, and the airplane was still shaking.
The speaker overhead started crackling, and the voice said 'Uh, this is the captain speaking. We are encountering a little patch of turbulence. I've turned on the seat belt sign. If you are moving about, please return to your seat.'
My Lady frantically tried to get buttoned up, and I just as frantically tried to get the inward-folding door open. Damn, that was a tiny space! How did we get in there? I finally got it open and ML stepped out and started rather shakily up the aisle. About that time the FA stepped to the center of the aft galley and looked me over.
'Please return to your seat and secure your seat belt, now,' she said, quite according to the book. 'Uh, right. I-My wife's shoulders were sore, I was just rubbing them. I-I'm going back to my seat now. I-uh-'
'Of course. Please go and sit down and buckle up, now.'
Whew! I sure fooled her. I'll bet she had no idea what we were really doing. Though when we were exiting next morning at San Jose' I did think she gave us a particularly pleasant smile when she said 'I hope you had a nice flight!'
My advice? The 'Mile-High Club' is a fun outfit to belong to, but try to be sure there's no mountain ranges to cross over or heavy weather predicted. Don't try it in a Boeing unless you're small people and not too fastidious about your surroundings. Go for an Airbus. The lavs are bigger and the doors open outward, just in case you have to leave in a hurry.