Hi, since I'm straight I can only tell you about encounters with girls...
Yeah, I had the 'classic high school sex' in the backseat of a car during a free period just like maaany other people on this planet

We (a great looking girl and me) went to my car and we did it. Just 10 minutes after I had sex with that girl (it was okay, but not thaaat great) it was time for lunch break and I went with another girl to my car and had sex. She was way better and sucked me off pretty good. That's the advantage of beeing single: having sex with whom you like whenever you like how often you like.
But here's another one I had recently with my actual gf. We were on a longhaul flight to Asia and had very short time to transfer at Singapore airport. That's why the friendly cabin manager upgraded us to business class, since those seats are in the front close to the exit doors and we'd be one of the first passengers to leave the aircraft so we have as much time as possible to transfer.
The business seats were fully flat and really cosy. For the night time all the lights were switched off and all people next to us asleep. Me and my gf were horny, but the toilets were right next to the galley and the flight attendends kept chatting there about stuff for hours. We didn't want to wait any longer, so I placed the thick blanket over me and she moved over to my seat. I moved her skirt and thong aside and slipped inside of her. She rode me as quiet and as inconspicuous as possible. I shot my load inside of her and she went to the bathroom to clean up. After that we were satisfied enough to have a small but good nap.
And
HERE'S the thing about it: After we disembarked the plane my dad walked next to me and the only thing he said to me was: 'I won't tell mom.' (My mom and my dad sat right behind us, but I was sos sure they were sleeping. Guess he was not.) I admit I was a little embarrassed.