Icons in 'ship details'

Sometimes when I bring up the details for a particular ship I see what looks like a space fighter icon (pointing up and left) but I don't know what it signifies. There are other icons, for a troop transport and for a constructor, which are more obvious. Often ships that are pretty much identical (even experience level) don't have this icon in common.

Any ideas? I'm guessing I'll kick myself when I realise what it means.