Yes, Jim is right!! My husband just flew back from PHL and he bought a full fare ticket quite last minute (but 4 days ahead of the return date) and the ticket was fully changeable, refundable yet we didn't find out later that it was a "B" fare in the return portion. One difference between a "Y" fare and a "B" fare in AA is that if you want to use miles to upgrade only a "Y" fare allows you to use 5000 miles for one way upgrade while all other fares will cost you 15000 miles. So, needless to say, he found out while trying to do upgrade that the return segment was a "B" fare. Make no difference in accuring miles, or using stickers.

Helen