Transatlantic flight 30 years ago, from Chicago in evening to land in Europe early the next morning. Met a lady in the bar, we struck up conversation and then juggled our seats to sit next to each other on the far side with an adjoining aisle/window seat combination.
More drinks and dinner on the flight. After dinner with cabin lights dimmed and blankets in place, I received a super HJ from the lady and then provided FIV pop for her. Lady across the aisle who saw that we were married and exchanging a lot of passionate DFK, then asked me if we were newly weds. I smiled and asked her how could she tell?
We arrived the next morning and my lady friend walked off aircraft to meet and hug her husband who was waiting, as I went off to my connecting flight further into Germany. We never exchanged names or numbers, just two lonely ships passing in a very hot, stormy night time encounter.
Over a thousand other flights, 5 million airline miles since then, and that's never happened again.