European plane maker Airbus filed a patent for a seating design that would literally stack passengers on top of each other. If it ever makes it to market, the layout could turn planes into a complex game of human Tetris.

The whole thing basically sounds something thought up by The Onion. And in fact, it was.

But this isn't the first time Airbus seating proposals have made flying seem like some form of modern torture. Last year, the company made headlines for filing a patent for a bicycle-like "sitting" arrangement that certainly didn't look like it would be comfortable over a long-haul flight.

And Airbus isn't alone: One major airline seat manufacturer grabbed attention in July after filing a patent for a honeycomb like setup that would leave passengers sitting knee to knee.

But plane designers aren't exploring these options just to make people uncomfortable. Instead, blame the democratization of flying.

Taking a plane trip has gotten an awful lot cheaper over the last 30 years, which is great because more people than ever are able to travel long distances to take vacations and see loved ones. But with the rise of less expensive flights and discount airlines, profit margins have gotten thinner. And one way operators can keep prices low is stuffing more people on a plane.

That's why airline seats keep shrinking.

But there's a limit to how narrow you can make a chair. If the industry wants to continue to expand the market of who can afford to fly, even more compromises will probably have to be made.

So expect to see more cramped and confusing plane seat patents in the future.