Originally Posted by
dkc192
Yep, 45k upgrade is your best bet. If you're on the 11am TBS-IST (which, as I said earlier, rarely if ever has upgrade space), go ahead with the upgrade through the website or app once you have the required miles, and don't bother with the feedback form to get both segments upgraded since TBS-IST very likely won't have space anyway (unless you can check and determine otherwise).
Thank for the advice here. Yup, I've done that TBS>IST flight at 11 in the past, and honestly, the flight is so short that being in Y is no big deal. The IST>ATL is the one I care about, so I'll see if I have the funds to pay for the 45k miles outright.