Do only recent flights count? If not... (because I cannot remember a single flight, apart from the last LHR-AMS hops, that have not been bursting)
SEA-LHR in February 1998 (continuing on to HRE). I was one of only 5 or 6 people in Club, and there was hardly anybody in Traveler (there was no WT+ back then). It was a night flight, and I remember it being very, very quiet and peaceful (even on the main deck), especially when aurora borealis appeared.
Sigh... those days seem pretty much over, at least for long-haul. Anyone else feel this way?
I once took a delivery flight too. That was also very quiet. And boring.