Was booking a flight on AA.COM earlier today and saw a screen I had not previously seen, nor had I seen mentioned on FT (apologies if I missed it). Just before the payment screen, the same one where you're offered the miles accelerator there was a box offering to "Guarantee Your Upgrade" and the price was NOT the fare difference it was ~$300 less than the lowest F option on the same flights (I went back after and checked the price difference). This was a domestic flight that's not long enough where I can buy F and I wasn't sure how it would show on the receipt so passed. Is this new or have I just never seen it before, wondering if anyone else got this offer and taken it and know how it shows on the e-receipt and if it books into revenue F for bonus EQMs or is it treated as an upgrade? I went back to the booking after ticketing to see if they would re-offer it but nothing.