Here’s a sentence that should change how you see every flight you take: Delta Air Lines expects to receive more than $9 billion from American Express this year. That’s not ticket revenue. That’s one bank paying one airline for miles — and it’s 1.4 times Delta’s entire adjusted operating income from actually flying planes.

Your airline is a credit card company that happens to fly planes. And the numbers prove it.

The money

Start with the big three, per a 2026 Reuters investigation and the airlines’ own earnings calls:

• Delta + Amex: $8.2 billion in 2025, expected to top $9 billion in 2026 — 14% of Delta’s adjusted operating revenue and 1.4x its adjusted operating income. Delta reports a 39% margin on SkyMiles. It’s the company’s most profitable business.
• American + Citi/partners: $6.2 billion in 2025 — about four times American’s adjusted operating income. Four times. The flying business is the side hustle.
• United + Chase: similarly in the multi-billions, with the partnership structured the same way.

The mechanism is simple: banks buy miles in bulk (estimated ~1.5–2 cents each), hand them to cardholders as rewards, and the airline books enormous, stable, high-margin revenue. Miles cost almost nothing to create, and plenty are never redeemed. It’s the best business in aviation — and it has nothing to do with aviation.

The programs are worth more than the airlines

A 2026 On Point Loyalty report put hard values on the programs themselves:

• SkyMiles: $31.8 billion — the most valuable airline loyalty program in the world
• AAdvantage: $26.7 billion — roughly 2.5x American Airlines’ entire market cap
• MileagePlus: $25.3 billion

Read that again. American’s loyalty program is worth two and a half times the whole airline. During the pandemic, carriers pledged these programs as collateral to raise financing — because lenders understood what investors sometimes miss: the program is the asset; the planes are the overhead.

As one consumer advocate told Reuters: “The modern airline is a gigantic rewards program that just happens to fly airplanes.”

Why your miles buy less every year

Here’s where it hits your family directly. The airlines have spent years rewriting the rules to favor card spending over actual flying:

• United now awards 3 miles per dollar on flights for non-cardholders versus 6+ for cardholders — and basic economy earns nothing without the card.
• American ended miles and Loyalty Points on basic economy tickets entirely.
• Delta ties elite status partly to Amex spending.
• Across the industry, the payback value of flight-earned miles has fallen roughly half since 2019.

The pattern is unmistakable: the person who flies is worth less to the airline than the person who swipes. Loyalty programs used to reward loyalty. Now they reward lending — you’re being cultivated as a credit card customer who occasionally sits in a seat.

What this means for your family

Once you see the business model, the strategy writes itself:

1. Earn miles from cards, not flights. The flying earns a pittance; the sign-up bonuses and category spend are where the miles live.
2. Don’t hoard. Miles are a currency the issuer controls and devalues at will — the 50% payback collapse since 2019 is the proof. Earn and burn.
3. The card IS the loyalty program now. If you’re choosing an airline for family travel, choose it for the credit card ecosystem, not the route map. The card determines what you earn, what status you get, and whether your basic economy ticket earns anything at all.

The bottom line

Airlines didn’t stumble into the credit card business — they rebuilt themselves around it. The planes are real, the routes matter, but the profit engine is a bank partnership and a database of miles. Fly accordingly: swipe smart, burn your miles, and never confuse a loyalty program with loyalty.