[sorry again! I think I'm *actually* here now!]
It's a polite, harmless question, and it sends alarms shrieking instantly down his nerves. Cassian knows - at least he's reasonably certain - that there's no need for them here, that he's not wanted even under his own name, that the kid is just a bored kid, that nothing's going to happen, but he can't stop his heartrate from jumping, even so.
He sits still, doesn't let his expression register more than mild startlement. "Um. I guess?" with a glance up the aisle. Don't make too much of it. "Seems like there are better candidates."