If you're on a flight -- especially a long one -- a coach class seat can be a chair of torture.

It doesn't take much these days to ruin a perfectly good airplane ride, CNN.com readers have made clear. It's a real buzzkill to try to walk down the aisle "with a bag on your shoulder, hitting everyone as you pass by," suggests user "Cajuncatdude." Commenter "Rosemeow" writes, "It's bad enough that about a quarter of the time, I have an obese person sitting next to me (sometimes on both sides) who doesn't fit into their own seat, crushing me."

And "MrsColumbo" complains about "people who don't even try to stand up without grabbing on to the seat in front and pulling themselves up. What is with that?"

For something as seemingly simple as stuffing rear ends between two armrests inside a flying metal tube, it kind of feels like there's some anger up there.

And things could get even more heated. Changes are happening now, as major U.S. carriers look for new ways to pump up profits by either adding to or reducing the number of coach seats, increasing legroom or cutting the distance between rows.

You might call it a game of aeronautical chairs that will directly affect passenger comfort, convenience and cost.

Two experts with inside knowledge of the airline seat industry-- a vice president at a seat manufacturer and a nationally recognized expert in the study of body measurements -- recently talked frankly about some of the reasons behind the anger and discomfort.

Are the seats getting smaller? Closer together? Are passengers getting bigger? Are we getting angrier?

Well, no. Yes. Yes. And it's unclear.

Americans are getting bigger, says Kathleen Robinette, who's studied human body measurements for the U.S. Air Force for three decades.

But in general, the problem's "not you -- it's the seat," she says with a chuckle.

Since Robinette's first airline seat study for NASA and the FAA in 1978, she has a different perspective when she boards an airliner. "I always see all kinds of arms hanging out into the aisles. That means the seats are too narrow, and there's nowhere for the shoulders and arms to go except into the aisle because there's not enough room in the seat."

When "you keep getting your arm whacked by the cart as it comes down the aisle," don't feel guilty, she says. It happens to everybody. "And it's because of the seats."

And what about passengers grabbing the seat in front of them to pull themselves out of their own seats? Is that really a thing?

"It can be quite annoying," laughs Jeff Luedeke, a vice president at airline seat manufacturer TIMCO Aerosystems, maker of seats aboard Allegiant, Japan Airlines, RwandAir, and Spirit Airlines. Seat grabbing creates a challenge for designers, said Luedeke, who flies about a quarter-million miles yearly. "If the rows weren't so close together that would probably prevent people from grabbing the back of the seat."

In 1962, the U.S. government measured the width of the American backside in the seated position. It averaged 14 inches for men and 14.4 inches for women. Forty years later, an Air Force study directed by Robinette showed male and female butts had blown up on average to more than 15 inches.

"The seat is a revenue generator," Luedeke says. "Normally if you look at a 737 or A320 there are three seats on each side. If you wanted maximum comfort you could do two on each side -- and make the seats a lot wider. But with the reduced head count the operational costs don't work out."

But the American rear end isn't really the important statistic here, Robinette says.

Nor are the male hips, which the industry mistakenly used to determine seat width sometime around the 1960s, she says.

"It's the wrong dimension. The widest part of your body is your shoulders and arms. And that's much, much bigger than your hips. Several inches wider." Furthermore, she says, women actually have larger hip width on average than men.

The industry used the male hip as a seat measuring stick "thinking that it would accommodate the women too, but in fact they don't accommodate the larger women."

The result: Airline seats are approximately 5 inches too narrow, she says. And that's for passengers in the 1960s, let alone the supersized U.S. travelers of today.

Current standard coach seat widths range from 17 to 19 inches between the armrests, says Luedeke, and that little piece of real estate is known in the industry as "living space."

The term seems appropriate for some non-stop transoceanic flights that will have you inhabiting your "living space" for up to 18 hours.

"I look at it like, I've leased this space for the next three hours -- or however long the flight is," Luedeke says. At a recent industry convention in Hamburg, Germany, TIMCO asked volunteers to test seats. The testers didn't know it, but some seats had cushions and some did not. Many of the testers laughed when they found out later that their seats had no cushions. Even funnier: Some passengers said the seats without cushions were more comfortable.