Focus of an airplane battle, maybe

ARMREST

Think of the part passengers might argue over during a long flight—it’s not the window or aisle, but something in between.

This clue plays on the double meaning of "battle." On the surface, it suggests a fight in the sky, like a dogfight between planes, but the real trick is thinking of a literal "battle" over space on an airplane—specifically, the fight for the armrest between passengers. The word "focus" hints at the object at the center of that struggle, which is the armrest itself. It’s a clever misdirection that turns a war metaphor into a mundane travel annoyance.