At first, I thought he was poking a little fun at me, but it became clear that he was serious. The shortest version of what I said in reply was, "No; it is a civilian space-liner."
He said, "Okay," and showed his military ID, "You see, I really am in the Navy, and I needed to make sure I didn't have to salute you."
I think I should take this as a compliment to both the outfit and to the way I wear it.