Ahypobaric chamber hides deep inside the research laboratories at Oklahoma State University. The university is located in an area that has an average temperature that regularly hits highs of more than 30 degrees celsius and is no more than 350 metres above sea level. For people locked inside, conditions in the airtight altitude chamber can be radically different.
During a seven-month period starting in October 2002 the chamber was fitted with 12 economy airline seats – each spaced 34 inches apart, around the average distance for seats on US planes at the time. Each morning a dozen willing volunteers entered the chamber at 10:00. Around 20 hours later, at 06:00, they were released from the sealed room.
Five movies were played on VCRs, a sleeping period took place from 23:00 to 17:00 and meals and snacks were provided. Unlike in conventional flights, the 502 volunteers who took part in the study weren't allowed alcohol to help them pass the time. Unlimited use of the toilets was allowed.
Each group spent their 20 hours at a differently simulated altitude: from ground level (198m) to a maximum of 2,438m (almost six and a half times the height of New York's Empire State Building).
The purpose of the elaborate setup? To determine what altitude the interior of an aircraft should be pressurised at. The results of the study, which was commissioned by manufacturing giant Boeing, found the cabin should be pressurised as if the plane was flying at 1,829m – or 6,000 feet.
"Of all the different features [of flight], pressurisation is probably the one that attributes to the reduced physical symptoms," explains Blake Emery, Boeing's director differentiation strategy who says the in-cabin altitude changes were applied across its 787 Dreamliner and 777x aircraft.
The 1,829m attitude point is the optimal condition for the human body – any higher and the amount of oxygen finding its way into the bloodstream drops by four per cent. Previously its planes were flying with higher levels of pressurisation – equivalent to altitudes of up to 2,438, (8,000ft). Emery claims the change reduces jet-lag.
The overhaul was one of Boeing's biggest in recent years. However, most aircraft changes happen on the inside. Airlines who buy, or more often lease, planes have a great deal of say of how they are kitted out. From seat numbers and configurations to lighting, toilets, and overhead bins, a plane can be customised to make flights better for passengers – and airlines.
Subtle alterations to their insides can make gigantic changes to how comfortable a flight is. And like Boeing's overhaul with the 787, most passengers won't notice the tiny modifications. "The space you have to play with inside isn't getting any bigger," Emery says. "The primary place you have to get those margins is the psychological dimension." And so the games begin...
Each time an airline buys, or leases, a new fleet of planes – mostly likely from one of the big three: Airbus, Boeing and Bombardier – they're faced with an increasingly complex set of design choices. "Every airline has a ton of customisation they can do," says Ben Kaufman, a marketing manager at budget airline Norwegian.
Interiors can be purchased as off-the-shelf packages or bespoke setups can be manufactured. And there's one commonality across all planes: every millimetre inside is worth money. So squeezing a better experience for passengers often comes down to design tricks.
"You're stuck with the format and seating densities, people need to make sure they get the seat numbers and the revenue correct," says Jeremy White, the transport director at London-based design firm Seymourpowell, speaking at the Aircraft Interiors Expo in Hamburg, where the industry has gathered to do deals and glimpse the future of airplane carpeting. "You're playing with the little things. The small things that can have big effects."
Take flyduabi's recent 737s. The planes, manufactured by Boeing, are a narrow-body airliner meaning there's normally only one aisle separating seats. Wide-bodied planes, by their very definition, have more space and have two separate aisles for passengers to move down.
"Traditionally on a 737 people don't fit in exciting products," says John Tighe of JPA Design. The firm specialises in luxury seats for business class flights and has done so since the late 1990s. On flydubai's 737s it adapted the Thompson Vantage seat, which folds flat into a bed. Tighe says the seats are traditionally installed in a 2-1-2 formation and put onto wide-body aircraft. But for a narrow body, where there's less space, the layout of the seats makes it appear the person in the middle seat has more space than fellow passengers.
"We raised the shell height and created a lot more consistency between the seat types," Tighe says. This, he claims, makes each seat feel more secluded and away from others. "The cabin feels a lot more balanced and even and the passengers have a higher level of privacy." In Singapore Airline's business class seats, JPA made it possible to lower a divider between seats and create a double bed. A honeymoon is a "dream scenario," Tighe says.
On other aircraft, space saving changes are even more subtle. White says using darker colours can stop a plane from feeling less claustrophobic. The technique of using dark ceilings is already popular in trains and cars, he says.
One constant frustration for passengers is baggage. Ingo Wuggetzer, Airbus' vice president cabin innovation and design, explains that during a recent survey he found 145 different baggage allowances on airlines around the world. As a result, a simple change of hinge mechanism is being rolled-out on Airbus' new A320 cabins. Wuggetzer says there are "minimum rotating parts" and the overall number of pieces used has been reduced. "The angle of the whole bin is a little bit steeper," he says.
"We lowered it in the back a little bit but lifted it up at the front. The loading height is the same but we pushed the ceiling up to get the suitcases in." The result? Airbus says it can now fit in 40 per cent more bags into its larger bins and that wheel-on cases can be inserted on their side rather than flat. The changes took 18 months to develop. And that’s just one hinge.
Elsewhere inside the A320, Wuggetzer explains, small changes have been made to the windows. "We gave the window bezel a shape that your shoulder fits in," he says. "If you sit next to the window it gives about an inch shoulder clearance."
For the human body, flying long-haul is an ordeal. Being confined to a single space that has limited fresh air, natural light and the freedom to move around is an alien environment. That’s all before you consider sharing the space with a few hundred people and their bodily functions and quirks.
When this is the case, the mind is a powerful thing. "It's really interesting to analyse how people perceive comfort: it's the light, the volume you get, sometimes the colours," says Patrick Baudis, the vice president of marketing at Bombardier.
Research by Boeing found that passengers flying on two almost identical planes – Norweigan's 737 NG and its 737 Boeing Sky Interior Aircraft – were happier when the aircraft had a wider entrance and better lighting. Boeing says passengers believed their seats and meals were better when in fact it was just their surroundings.
But the chance for making radical design changes to improve the hours passengers inflight are reducing. "The low hanging fruit is disappearing," JPA's Tighe says. "If you took a catalogue seat from ten to fifteen years ago in some ways it was an easy job for a designer because you could get a hold of a model, put some 3D sections through it and spot badly used spaces that could be used better," he adds. "Now it is harder to do that."
Instead Tighe is looking towards the "unusual" things people do while flying to come up with new design tweaks. To make these advances – some of which involve moving parts by just millimetres – human behaviour offers the most potential. "Lots of passengers in an economy class seat put their feet in the literature pockets," Tighe says. "People find comfort in lots of different ways that the engineers and airlines don't necessarily expect." And by better understanding that, designers will hope to keep making those marginal gains.