As mwenezi says, bidding for upgrades is something a lot of airlines are currently doing
In LATAM it's been rolled out very silently and on some routes only. For reasons I'm yet to find out, it's only sometimes available on all LATAM.com localized sites (and it has been available in Chile, I have used it a couple of times)
The available routes do vary. SCL-MEX and MEX-SCL has also been available (which is where I used it)