As of 2011, FCO was the third largest international destination not served by Delta, behind FRA and PVG. I haven't seen more recent data, but FCO and PVG were climbing, while FRA was sinking. With a SkyTeam hub in FCO, I wouldn't be at all surprised if FCO is higher yielding than FRA. As for PVG, I doubt Delta has the available equipment for that route. And it's still bolstering LAX-PVG as well.