Originally Posted by SenSCL

Only flights operated by LA and booked under their own flight number qualify for upgrades (assuming that you are referring to an upgrade via the unlimited number of coupons for Black members). Furthermore, these have to be from the Plus or Top fare baskets (this can be tricky to find out, when you book your tickets via an OTA or any other channel that is not the LATAM website). In the past, the qualifying fares were easily distinguishable by the corresponding letters, but this seems to have changed, although the letters, traditionally used by most airlines for the higher value Economy fares like M, B and Y, have always been upgradeable fares, at least in my experience. LATAM actually also allows to upgrade tickets purchased with their miles (LA flights that is).

In summary, you can upgrade the LA portions of your OW RTW ticket, provided that the above criteria are met. Of course, you have to take into account that as a Black member, you have a maximum of six coupons to spare for travel companions and flights to and from outside Latin America do require a minimum of two vouchers (best value for this very amount is probably LIM - MAD or LIM - BCN, especially if you can get the new business class product on the B767).

I hope this answers your questions at least partially.