Fascinating. Let me explain how this word ended up on my list (and yes, the best synonym, and certainly what I intend when I use it, is air sandwich).
I came across it relatively recently, reported to me from a conversation about concert programming. A concert (I don't know which one) for an orchestra (not mine) was described thus by its creator(!). And it just struck me as a wonderfully apt phrase for the kind of concert program (I'm surmising here) where there are various nice things to be heard, but no actual meat, nothing to make that concert compelling for the audience and musicians. So I think I will use it myself when suitable occasions arise, while simultaneously hoping that they rarely do!
I know other people who go to Burger King (you would know this as Hungry Jack's, bilby) and order a "veggie burger," which, so far from being a burger made of vegetables, is actually just the bun, and the condiments and vegetables that are normally placed on the burger.
To me, that's gross. I think it's the thought of ketchup and lettuce together with no ameliorating substance between them.