That's a pretty tough route to get low level biz on. I went to BCN in September with the family in J, so I spent a fair amount of time searching that route. DL only flies two direct routes from USA to BCN, one being from ATL and the other from JFK. I did see some availability out of JFK on the direct flight to BCN while searching, so you might have better luck there if you don't mind the connection.

If you don't mind connections, then start looking for Air France availability or KLM availability routing through AMS or CDG. AF has a lot of flights on CDG-BCN, so it should be easy to get there if you can get to CDG. Alitalia out of JFK through FCO is another good option. I had my sister fly that on her way home, and my parents did it from LAX.