Thanks for the replies!

I read the nonrev article but still have a few questions

I am assuming that Flower's post indicates that I can fly into madrid and out of barcelona on one buddy pass....Is this correct?

Also,

Is there a way for a non airline employee to check which seats are available for a particular flight? Simply going to Delta's website doesn't seem to give an accurate picture.

How about looking at the typical seat load for wednesdays or thursdays in September historically for an ATL to Madrid and then a Monday return from BCN to ATL. Is this possible?

Thanks for all your help!