Do you understand the difference between a cash loss and equity write off? As in, they didnt really lose 12B out of their bank account. A lot of it was a "paper loss". Delta played accounting games and lumped asset depreciation for years to come into last year, among other things (Early retirement payouts, investing in their pension so they'll be self funded, JV equity writeoffs). If you are going to take a loss, take them all at once approach. This sets up future years for no tax liability, and manages the stock price volatility for future quarters. They wrote off the value of 56 767s and 91 717s to the tune of several billion, but they'll still be flying most of them til 2025. Still today taking most new aircraft in cash. Most of their debt will mature in short term.

They reduced a lot of future cost headwinds.
I foresee them quickly getting cashflow positive, paying down debt to 2019 levels (10B), and making billions a year in profits. May take a few years.