You thought airlines sold seats. Cute.

Imagine you’re sitting at Starbucks.

No airport.

No suitcase.

Not even mentally prepared for security screening.

You buy a coffee with your Delta American Express card.

And somewhere inside that transaction…

Delta just became interested.

Because modern airlines have discovered an excellent business:

Make up their own currency.

Sell billions of dollars of it to banks.

You know the currency as airline miles.

In 2025, Delta received $8.2 billion in cash from American Express through its SkyMiles partnership.

That was roughly 14% of Delta’s adjusted operating revenue — and about 1.4× its adjusted operating income. Important caveat: that $8.2 billion is cash from the broader AmEx partnership, not $8.2 billion of pure profit, and some revenue is recorded later when miles are redeemed.

(Small banana peel: the $8.2 billion covers the broader AmEx partnership - it isn't $8.2 billion of pure profit.)

Still
eight point two billion.

Your frequent-flyer program is not the little freebie department sitting next to the real airline.

It is very much part of the real airline.

Say your credit card promises:

Those miles do not emerge naturally from the financial ecosystem.

American Express gets them through its relationship with Delta.

Delta’s own filings say companies including credit-card providers, hotels and retailers purchase miles from Delta, with American Express being by far its most important such relationship. Payments are typically made monthly based partly on the volume of miles sold.

So the basic machine looks like this:

Beautiful.

Because the fake airplane money gets you to choose their card.

And then hopefully use it.

A lot.

Banks can make money from card fees, merchant fees and, depending on the product and customer, interest and other financial services.

The airline brings something extremely useful to the relationship:

you really want that trip to Japan.

So instead of advertising:

they can advertise:

Much sexier.

And this has become so important that airlines are increasingly designing loyalty programs around credit-card spending, not simply how often you sit on their planes. Reuters found several major U.S. airlines have been shifting rewards toward cardholders and higher spenders.

Miles look like money.

They are not quite money.

With dollars, Starbucks cannot wake up tomorrow and announce:

Your airline has considerably more flexibility.

It controls how miles are earned.

How they're redeemed.

And how many miles that Sydney-to-Tokyo seat costs.

Industry research cited by Reuters found the reward value passengers received from some U.S. programs had fallen substantially since 2019.

So points can absolutely be useful.

But don't spend $1,000 you didn't need to spend because a little progress bar told you you're 7,422 miles from Platinum Banana Diamond status.

And definitely don't pay serious credit-card interest to earn a flight you could have bought with cash.

Frequent-flyer programs started with a simple idea:

But airlines eventually discovered something better.

They can make money from you even when you aren't flying.

Buying groceries.

Ordering dinner.

Paying for petrol.

Sitting at Starbucks thinking about a holiday you haven't booked yet.

The airplane used to be how you earned the miles.

Now the miles help make money whether you're anywhere near the airplane or not.

Turns out one of the most valuable things an airline can put in your wallet…

isn't a boarding pass.

It's the card.

The monkey will never look at “free miles” the same way again.