The Volokh Conspiracy

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Knee Defenders and Virtual Laps—Part 2

There never used to be fights over reclining airline seats. Why are they breaking out now, and what does this tell us about the hidden rules of ownership?


Credit: Wikimedia.

This post is adapted from our new book, 
Mine!: How the Hidden Rules of Ownership Control Our Lives, available March 2. To learn more about the book, visit

Yesterday, in Part 1, we introduced the Knee Defender and the three conflicting ownership stories—attachment, possession, and first-in-time—that passengers use in high-altitude fights over inches of personal space.

Why are these conflicts breaking out now? There never used to be rage around reclining. Until recently, airline seats had greater pitch, or space between seats—enough both for reclining and for lowering the tray table. No one thought to ask who controlled the space because it didn't much matter. But airlines have been shrinking the pitch in economy class, down from 35 inches not that long ago to just 28 inches on some planes.

There's a lot at stake for the airlines: one inch of pitch saved per row can add up to six extra seats per flight to sell. To grow profits, airlines are squeezing ever more passengers inside a fixed steel tube—at the same time that people are growing bigger and tray tables have become precious computer stands. The stakes are high for passengers as well. In the COVID-19 era, each inch of personal space can feel like a life-or-death matter. So, passengers get angry at each other. But why aren't they angry at the airline?

It turns out neither Beach nor Williams really owns the wedge of reclining space. The airlines do. And they are savvy pros at ownership design. As Ira Goldman, the inventor of the Knee Defender (whose website traffic increased five-hundred-fold after the Denver flight incident), described: "What the airlines are doing is, they're selling me space for my legs, and they're selling you the space—if you're sitting in front of me—they're selling you the same space to recline. So they're selling one space to two people."

Can the airlines do that?

Yes. In 2018 the Federal Aviation Administration declined to regulate airplane seats, leaving their design to the airlines. In turn, the airlines use a secret weapon that lets them sell the same space twice on every flight. The weapon is strategic ambiguity, a sophisticated tool of ownership design. Most airlines do have a rule—the passenger with the button can lean back. But they keep it quiet. Flight attendants don't announce it.

Ambiguity works to the airlines' advantage. When ownership is unclear—and it's unclear far more often than you might imagine—people mostly fall back on politeness and good manners. For decades, airlines have counted on high-altitude etiquette to defuse conflicting claims. That's why Delta CEO Bastian said you should "ask if it's okay" to recline. Passengers negotiate among themselves as they angle ahead in line, nudge elbows over shared armrests, and jostle for overhead bins. Money rarely changes hands. (One study, though, suggests about three-quarters of passengers would agree not to recline if the person behind offered to buy them a drink or snack.)

But as airlines continue to shrink the pitch, unspoken rules over the front-to-back squeeze are breaking down and everyone ends up looking unreasonable. Goldman saw ownership ambiguity as a business opportunity and created a technological solution. The problem, though, is that a unilateral move to lock the seat violates customs of politeness. It feels like taking something without asking.

The Knee Defender may seem like a silly novelty item, but it reflects one of the great engines for innovation in our society: as valued resources become scarcer, people compete more intensely to impose their preferred ownership rule, and entrepreneurs find ways to profit.

In post #3 tomorrow, we will introduce another ownership puzzle: why does New York City have some of the world's best drinking water?