Originally Posted by Bowgie

1. Since a few years ago, Delta ended mileage upgrade awards to Mexico, Caribbean, and all of Central America and South America.

2. On certain dates (as above for example), Delta.com will only show ridiculously expensive refundable PS, which is almost as pricey as straight-up non-refundable DeltaOne. The actual non-refundable (cheap) PS fare is actually bookable, but one has to either call Delta, or find it on Google Flights and click-through to Delta.com's "buy it" page. This is an amazingly stupid example of Delta.com's non-functionality.

3. Premium Select (non-refundable) is as low as $1560 to Santiago and about $2200 to Buenos Aires (from SAN and connecting thru ATL). Neither fare is cheap to me, but still useful if one wants to instant upgrade. (Must call-in, or book PS with agent and have agent apply the GUC.)

4. If one is calling in to book a "G" (cheapest) PS fare and hoping to apply instantly a GUC; the availability of upgrade space (OY) is correlated with the revenue DeltaOne fare being (Z). There are probably counter-examples, but this was the case for my last four or five bookings.