Until the next recession, F upgrades will be rare, and as a business case, that most likely makes sense for Delta. UA seems to be pushing FCM as well.

The question I have as an investor: is this encouraging brand-switching? And by that I don't mean "I am pissed I don't get upgrades anymore, I'm switching to xxx airline where the grass (may be) greener" but rather, "I am booking as much paid-F as I can budget, and will fly whoever offers the best value/service/schedule mix on any given flight."

It could be that enough UA FFs (and some AAs?) will do that to so that both UA and DL manage to increase yields, poaching each other's brand-switchers. But the airlines are projecting lower yields for 2016, and it is very difficult for average investors to decipher how much of that is the global slowdown & continued pressure from ULCCs, and how much might be decreased loyalty leading to more rational price-based shopping by frequent travellers/late bookers.