BCN is not a great spot because so many flights are on Vueling, which won't count in AAdvantage. I'm almost positive that the only IB metal flights out of BCN are to MAD, although there may still be some European flights on Air Nostrum which also count as IB.

BCN-MAD-LIS can be a good option. Also the BCN-LGW hand baggage only fare on British Airways.


But as mentioned above, all you really need to do is put in a bit of effort and run an ITA Matrix search for your dates with a bunch of Spanish airport codes like BIO, SVQ, AGP, VLC, PMI, ALC, SCQ, etc.

There is a fare sale at the moment for 35 euro one way flights in the Spanish peninsula. Most likely you will want to get yourself to MAD on one of the first flights of the day, then fly back and forth to wherever, then catch the last flight back to BCN...