That clip they showed on Jimmy Fallon is telling.
Alex asks Tommy what’s wrong with his friend. Tommy responds he’s looking for a way out in case the ship goes down. Alex’s face and mannerisms indicate he hadn’t thought of that and wonders if anyone else around them has thought of that. He and Tommy silently communicate that the other soldiers aren’t taking precautions and they start to casually move towards the door, both of them thinking the same thing; the ship could be hit and will go down if it is, we should get near a door so we aren’t trapped. They say nothing to anyone else.
This scene should tell all of us exactly the type of character Harry is playing and what Alex’s motivations are. I didn’t get that the first couple times I saw it. Very clever to release that clip.