Never received an op-up on an any international flight (but I've seen it happen), but I have had several upgrades happen as a result of just being nice to the GA's, like after asking if I could change to a different flight at ATL after flying in on standby a day early.
Most memorable was actually an upgrade for my wife, a few days after I became Gold Medallion on Delta. We were flying SMF-SEA-ANC on Friday and I had been upgraded to first at the window for all flights (holiday weekend). Gave wife my seat for SMF-SEA and sat in the back. At SEA I figured what the heck, I'm just going to ask the GA (who was trying to get the flight out on time) to see what was possible. Lined up at the podium and in front of me were several people yelling at the GA how they had to have seats together otherwise it would be awful and their kids (in their teens) would misbehave and bla bla bla. She sent them on their way but others in the same group were right behind me. I got up to the podium as she was trying to get seat assignments for everybody and just said "hold on". I waited for about 5 minutes before even saying anything. As she finished up she asked what she could help with and I politely asked if there was any chance for my wife to be upgraded as well so we could sit together. Couple of keystrokes later and a "usually it's never possible but you held back the line for me" and we were both in F.
Those flights were my wife's first experience ever flying any kind of premium and I'm afraid she will refuse to fly in the back from now on, so this weekend trip to Alaska might turn out very expensive. Oh well. Anything to keep the wife happy
(flying in J to LHR next week).
Dennis