Most businesses would kill to be in the position Delta is - the ability to print their own currency on an enormous scale.

Doubly amazing that this currency is never redeemable to cash but instead but be redeemed for excess inventory at close to zero incremental cost. (Or in terms of pay with miles, redeemed at less than issuance cost, with additional giant subsidies from Amex for the privilege)

Most importantly, it serves as a very effective loyalty incentive, motivating brand loyalty and switching costs in an increasingly commoditized industry via "status".

If the value of delta miles/status decreases, I'd argue their brand value does to an even greater extent. They will never win in a battle of "buy the cheapest fare" ota customers, and they must understand it at some level, hopefully.

I'm sure there are quants crunching profitability spreadsheets, but number crunchers have destroyed plenty of good businesses in the past.