LB: “With one parent going in the quiet adult section.”
It’s only adults who are travelling without children who would request the adult-only section.
If anyone uses it your way, they clearly have shalom bayis issues to begin with. Or else, one parent just really needs to get sleep more than the other for whatever reason. Maybe, he (or she) is going on a speaking tour when they land, or maybe he (or she) has CFS, etc. But in that case, presumably this is something they discussed and decided was necessary. And if not, they need marriage therapy anyhow.