Every so often, officials at Rockwell Collins Inc. pitch a one-day job offer to residents near its Winston-Salem, N.C. design center: Earn $100 for sitting in an airplane seat for eight hours.

Show up for the gig, and there’s nary a drinks cart or flight attendant in sight. The rows of seats are arrayed in a testing area at the company’s design and engineering complex. Even without engine hum or overhead bins, “it’s kind of like they’re on the plane,” says Alex Pozzi, vice president of research and development at the company’s campus here.

Over the years, seat researchers at B/E Aerospace, which Rockwell acquired in April for $8 billion, have gleaned a few insights about life in the air. Most people are just fine for two hours. As the third hour approaches, stiffness increases and comfort declines. At four hours, however, a sort of derièrre detente is achieved, and the levels of discomfort recede. After all, when you’re stuck inside a sealed, speeding tube at 35,000 feet, resistance is truly futile.

There are many reasons to despise flying, from delays, to fees, to overzealous TSA staff. But shrinking seats and the pain, claustrophobia, and rage they can trigger are arguably the biggest reason why travelers loathe airlines. The modern seat, with its power to pack more customers onto any given plane, is at the very heart of the industry’s 21st century economics. Slimmer seats and less legroom between rows—known as pitch—has enabled “cabin densification” across domestic and international fleets. More seats, quite simply, means more money and lower operating costs.

There are limits, however, even beyond physical constraints. Regulators mandate a certain ratio of attendants to seats, and carriers want to keep labor costs down. Still, the trend has clearly been moving toward scrunching you. While 34 to 35 inches of pitch was once common for economy class, the new normal is 30 to 31 inches, with several major carriers deploying 28 inches on short and medium flights. Soon, however, that squeeze-play may come to an end.

The seat factory in Winston-Salem is at the center of testing the physical limits of human tolerance. One part of its live studies involves giving only some participants Wi-Fi access, an exercise that typically reveals a direct relationship between distraction and seat-staying power. “You can easily see the difference in ratings for the exact same seat if you have entertainment,” says Pozzi.

Yes, a good sci-fi flick can ease the harshest heinie-holder, and it’s no coincidence that most seatbacks on long-haul flights have a screen. But this is small compensation for the sacrifices required of air travelers who, having run the gantlet of parking, ticketing, security, and terminal, visibly slump when they find that their assigned seat has gotten even smaller.

Let there be no doubt about the shrinking quarters in economy—space is tight. Reallocation of aircraft real estate has allowed airlines to install new, medium-tier cabins between first class and economy. The front of the plane where the big money sits remains largely unchanged when it comes to space. The shrinkage, unsurprisingly, has been in back.

In recent years, the “slimline” seat has become the de facto standard by which airlines outfit economy cabins. This design is inches thinner than predecessors and markedly lighter, allowing carriers an additional cost-saver by reducing weight and thus fuel burn. Today, an economy seat that tips the scales above 9 kilograms (20 pounds) is, by an airline’s measure, too heavy to fly.

Carriers are “segmenting the economy cabin into two or three buckets,” said John Heimlich, chief economist at Airlines for America, the industry’s U.S. trade group. These efforts help “to minimize the market-share loss to ultra low-cost carriers [ULCC] or to other modes of transport.”

When Boeing Co. introduced the twin-aisle 777 in the mid-1990s, a nine-seat breadth was standard. Now, the aircraft—flown by carriers worldwide—often seats 10 across in economy, making life even more miserable for passengers. Boeing’s 787 Dreamliner has become notorious for its economy-class pinch with nine across-seating—and on some 787s, these seats are only 17 inches wide. (Airbus’s new A350 is also typically configured with nine seats across, but its cabin is about four feet wider, so it could fit 10.)

This cabin squeeze and seat-shrinking has helped increase earnings in an industry that’s gotten used to fiscal stability. But it occasionally results in some bad public relations. Two United passengers got into a kerfuffle in the summer of 2014 when a man stuck a “knee defender” device on the seat in front of him to prevent reclining, causing the seat’s occupant to grow irate. The crew diverted the Denver-bound flight to Chicago to eject both combatants.

In early May, news leaked that the world’s largest airline, American Airlines Group Inc., planned to add three rows of seats separated by only 29 inches of pitch on its new fleet of Boeing 737 Max, which arrives later this year. That arrangement would allow for an additional row of extra-legroom seats, which American calls main cabin extra, between first class and steerage. The move would have broken the current 30-inch pitch limit among the six-biggest U.S. airlines, putting it closer to no-frills carriers such as Spirit Airlines Inc., which offers a mere 28 inches.

Less than six weeks later, American reversed course—not because of passenger outrage, but because of flight attendants. American Chief Executive Officer Doug Parker said on July 28 that employees pushed back at having to be the front-line defender of a new level of cabin-class stratification. Parker said employees were telling him, “‘You’re going to put us in a position where we need to explain to these customers that indeed this is necessary so that we can have one more row of main cabin extra?’”

Parker explained the underlying calculation: “While we could convince ourselves that that might be able to produce somewhat higher revenues on the aircraft, what it was doing to our perception with our team wasn’t worth it.”

No airline has yet edged below 28-inches of legroom, although at least one major seat manufacturer, Zodiac Aerospace, has shown a prototype designed with just 27 inches. Italy-based Aviointeriors SpA gained attention in 2010 with a “standing” perch-style concept called SkyRider. That “seat” hasn’t passed regulatory muster, nor won any orders, although periodically a ULCC will speak favorably about such seating possibilities. Last month, South American carrier VivaColombia was the latest to raise the prospect of standing flights.

This rush to squeeze ever-more money out of passenger posture may soon slow. Carriers such as Delta Air Lines Inc. are looking to exploit this issue by retaining some creature comforts its competitors have ditched. It’s kept nine-across seating on its 777s, “one of the only in the world” to do so, says Joe Kiely, Delta’s managing director of product and customer experience. Delta has also led an industry trend to fly larger aircraft on more routes, reducing the role of regional jets. JetBlue Airways Corp. took pitch into consideration for its Airbus A320 fleet, which will see legroom shrink by more than an inch, to 32 inches, starting this fall. Despite the contraction, JetBlue wanted still to be able to advertise “the most legroom in coach.”

Meanwhile in Europe, low-fare king Ryanair Holdings Plc will pitch its 197 seats on the new 737 Max at 31 inches—one more than American, which plans for 30-inches of legroom in a slightly smaller version of the new 737 it begins flying in November. The battle over comfort, or more accurately less discomfort, is on.

Smaller seats and legroom have come in for scrutiny by a powerful federal appeals court. A three-judge panel recently ruled that regulators must consider setting minimum space standards, agreeing with aspects of a consumer group lawsuit that warned safety is being compromised. In emergencies, the Federal Aviation Administration requires fully loaded planes be emptied in 90 seconds or less.

“This is the Case of the Incredible Shrinking Airline Seat,” U.S. Circuit Judge Patricia Ann Millett wrote in the July 28 ruling. Her court, the U.S. Court of Appeals for the District of Columbia, handles most cases involving federal regulators and rules, a fact that may give airlines pause as they decide whether to shrink seating further.

Flyers Rights, a nonprofit advocacy group, contends that seat space has shrunk at the same time passengers have gotten larger. Those developments could lead to a catastrophic outcome during evacuation, the group warns. It also points to a less dramatic peril exacerbated by tight quarters and longer flights: deep-vein thrombosis, or blood clots in the leg, which can kill.

“Our concern is that it will take a Titanic-type disaster to make a change if we don’t get regulation,” says Paul Hudson, the group’s president. The court decision may “give impetus to getting seats back to where they’re going to be both safe and potentially not unhealthy.”

Bills pending in both houses of Congress would mandate rules on minimum airline seat space. In the past, such efforts have failed; the U.S. Department of Transportation has likewise been reluctant to address the topic. Airlines frequently say that such regulatory moves targeting key revenue centers—baggage fees, seat space, ticket-change fees—could lead to higher fares. Hudson, who previously worked as an aviation attorney, dismissed the industry response as a knee-jerk reaction.

“I’ve never heard that argument not raised,” he says

Airlines offer a few other rejoinders to the chorus of complaints. One is airfare: Faced with a choice between discomfort and higher fares, an overwhelming majority of travelers choose the former. Another is pricing-power. While industry consolidation did allow carriers to cut costs and command higher prices on some routes, average U.S. airfares have been one of the few consistent goods to hold firm against inflation over the past 20 years. Slimming the seats and tightening the space, the airlines argue, is a rational response.

The industry also points out that new seats, while thinner, are far superior to older models. Carriers’ zeal for lighter, durable, ergonomic seating has yielded engineering advances. Body shape and size, along with better materials and design, have become integral to airline seat manufacturing, and all four of the industry’s major players—Recaro GmbH, Thompson Aero Seating,  Zodiac Aerospace, and Rockwell Collins—are fiercely competitive in such areas as materials and ergonomics.

The L-shaped seat of yore has morphed into something more akin to a pivoting cradle-chair, seat designers say. And the once-flat seat pan, the chair’s frame and source of much anguish, is now generally curved. The passenger’s lower back is also finding fresh support in the newer designs.

American noted repeatedly that its seat selection for the 737 Max is a newer Rockwell Collins design, called Meridian, that’s more comfortable than prior economy-class seats. That’s the same seat Southwest Airlines Co. chose for its 200 new Max aircraft and its current 737-800s. United Continental Holdings Inc. is also purchasing the Meridian seat for its Max 9.

During a tour of its Winston-Salem design complex in May, Rockwell Collins officials invited reporters to sit in a variety of newer seats, including the Meridian and Aspire, a model aimed at two-aisle aircraft on long-haul routes. Tom Plant, vice president and general manager of aircraft seating at the company’s Interior Systems unit, asked the “passengers” to guess how much legroom each seat had. The pitch was 29 inches, but all the guesses were too high, mostly 30 to 32 inches.

Designers had managed to create a clever illusion of space. And that illusion means money.

©2017 Bloomberg L.P.

This article was written by Justin Bachman from Bloomberg and was legally licensed through the NewsCred publisher network. Please direct all licensing questions to [email protected].

Photo Credit: Southwest is one of many airlines introducing slimline seats. They allow carriers to pack more passengers in the same space but some travelers find them uncomfortable. Southwest Airlines