I was browsing Aviation.SE site when I noticed "+10" on the reputation dialog. I clicked on the achievements icon in the top nav bar to see what I got that rep for. It was for a answer on Stack Overflow, but that's irrelevant. Also in the drop-down achievements panel were listed a couple of my recent badges from SO - but with an icon for the Aviation.SE - see the screenshot below.
Of course, there's a site icon indicating which site the badges were for, yet I was confused for a second when I saw a little plane badge.
So, is this a slight oversight/bug or an intended behavior?