I suppose it also depends on what kind of outfit you are being interviewed by. An airline will probably expect the more conservative approach (even the likes of easy with their 'informal' culture still have flight crews in shirts and ties not t-shirts and jeans), but some non-airline GA outfits or flying schools may be more amenable to a smart casual approach.
I'm a traditional old fart and haven't the guts to go without my best suit and tie.