Originally Posted by
thelostshark
I can understand that for things where they have physical inventory that they mail out, but not for everything. For example, why would UA miles go out of stock, as they did recently for the 10k Mypoints/5k UA miles option recently? It's not like they're mailing you a gift card. tls
I suspect that they buy miles from United in bunches and once they run out then they have to buy more (once they are motivated / have enough money).