popa: Perhaps it may not be their fault, but they should still apologize. It’s just common derech eretz- even if it’s not your fault, you apologize. Reality is 95% other people’s perceptions- we DO need to be careful of what we look like, and even when a Jewish person does NOTHING WRONG, it can be a chillul Hashem if only because that’s what people think it is.
Honestly, they could have been the victims of an anti-Semitic attack or they could have been a bunch of cackling hyenas, but all I know is that I shudder to think of what my grade would be like on a public plane.
(Sorry, love ya guys, but be real here.)