Originally Posted by
gemac
No on domestic flights.
On international, there was a girl from the Duty Free Shop with a cart of bags waiting for our JFK-BCN to start boarding last week. I didn't hang around to see what became of the stuff, I assumed she got it on board OK but she was still there when I got on the plane (I was first to board).
Duty-free customers pick up their bags from the cart just before they get on board.