Very interesting....and informative. When I look at any test BOS-SXM flight I do not see the Blue Plus fare and, in fact, I have never seen that fare listed. I stand corrected that it does exist but not on any of the flights I have looked at or booked. Blue Plus is also not on the fare comparison page that I saw (and posted) on their website yesterday which is obviously different from what you saw

I guess if it is available use it...if not, well that's that