Last month I wrote that airlines have an opportunity to raise cash through their frequent flyer programs. These are big assets that they could sell a stake in, as several other airlines around the world have done. The largest airlines have multi-billion dollar annual deals with banks, and at some cost they could accelerate some of that cash.

In the years following 9/11, as airlines struggled, and again during the financial crisis airlines pre-sold miles to their credit card partners at a discount in order to raise cash quickly.

United and Delta each pre-sold miles, the former for about $500 million and the latter twice totaling about $1 billion. American did it too with Citibank. These ‘cheap miles’ paved the way for banks to offer big bonuses to consumers both for acquisition and for ongoing spend.

Now United and Delta are having similar talks again around “selling miles in bulk to their credit-card partners to raise cash.”

United Airlines Holdings Inc. and Delta Air Lines Inc. and their respective credit-card partners, JPMorgan Chase & Co. and American Express Co., have discussed unloading miles ahead of schedule and for less than the lenders would ordinarily pay, according to people familiar with the matter.

…The banks would—all at once, and at a discount—buy miles they otherwise would have purchased in the future as cardholders accrued points. The cash infusion could help keep the airlines alive, protecting card partnerships that generate billions of dollars of annual spending volume.

Deals like this sacrifice future revenue for liquidity today. On the other hand, miles sold today won’t be redeemed until farther into the future either.

It’s no coincidence that United and Delta are reportedly in these discussions, but there’s no public rumblings about American yet doing the same.

• A year ago Delta extended their agreement with American Express to 2029 while United got in just under the wire extending their deal through 2029 before the bottom fell out of the industry. (United likely leveraged a threat to pull out of Chase Ultimate Rewards point transfers to get their deal.)

• American finds themselves in a different situation. having struck a new deal with both Citibank and Barclays in 2016. They’ve been in discussions to renew their agreement with both banks, however they do not have a new deal. That makes it harder to pre-sell miles for future use, since there isn’t yet an agreement on future use. And it potentially gives Citi, which has deeper pockets, leverage in negotiations if they were looking for exclusivity.

When airlines rush to put passengers back in seats, they’ll turn to their frequent flyer programs to do it. We can expect big bonus promotions, and printing more miles than ever. That works while planes are empty, and there are plenty of redemption opportunities. But as planes fill up again we’re likely to see airlines devaluing their programs, requiring more miles for the same seats.

Hopefully this time credit card companies will write better contracts that allow them to prevent their big mileage purchases from being inflated away, because the standard language most banks have used for this purpose haven’t worked.

Of course the federal government shouldn’t have been a lender of first resort with a bail out. Airlines should have been expected to tap all available liquidity before going to taxpayers. They’re only now beginning to talk about doing that with their loyalty programs.