Ever wonder why nearly all planes have blue seats? You've probably never noticed. Or why brand new models are still equipped with ash trays when it's illegal to smoke on board these days? Well wonder no more. Here we unpack some of lesser-known facts behind the design of an aircraft cabin.

Why seats are generally blue

From Ryanair and British Airways to American Airlines (the world’s largest carrier), airlines across the board incorporate various shades of blue in their cabin seats, and it’s no coincidence. There does appear to be some psychology behind it.

Blue is associated with the positive qualities of “trust, efficiency, serenity, coolness, reflection and calm,” according to Colour Affects, the London-based consultancy run by Angela Wright, author of The Beginner’s Guide to Colour Psychology.

Nigel Goode, lead aviation designer and co-founder at Priestman Goode, which has been delivering aircraft interiors for 30 years for airlines, including most recently the Airbus Airspace cabins, states: "Our job as designers is to reinforce the airline’s brand and make it more recognisable, but our primary concern is to deliver an interior that maximises comfort to create a pleasant environment.

"Blue became the colour of choice because it’s a conservative, non-contentious, corporate shade" Credit: AP

“It’s all about making the travelling experience less stressful and blue is said to evoke a feeling of calm. While some of the more budget airlines might use brasher, bolder shades, most others go with muted tones. The overarching aim is to create a home-like relaxing feel, so airlines tend to use muted colours that feel domestic, natural and earthy for that reason."

It's also a trend that emerged decades ago and has simply stuck, he added: “Blue became the colour of choice because it’s a conservative, non-contentious, corporate shade that symbolises being trustworthy and safe, so you see it used in all of the older airlines like British Airways.”

Several previous studies have indicated strong links between colours and consumer perceptions of a brand, including one where researchers found that up to 90 per cent of snap judgments about products are made based on colour alone, Psychology Today reported back in 2014.

The science behind the lighting

Cabin lighting is also geared towards creating a stress-free atmosphere on board, particularly in newer planes which have introduced soft LED lighting to replace the harsher light used in earlier models.

“There is definitely a science behind getting the right lighting on board, looking at the mix of colours used on board and how the light will reflect off the thread of the fabric," Mr Goode explained.

The Airspace cabin interior on A320neo

Once all of the fabrics, textiles and finishes have been chosen, several colour workshops are held on aircraft interior mock-ups to trial the settings across a range of different lighting scenarios, from boarding and when pre-meal drinks and meals are served, to the sleeping hours.

“We work with lots of CMF (colour, materials and finish) specialists who look at various textiles and put a lot of work into choosing the best colour for the lighting. We want to make the seats restful but also somewhat interesting and not too bland to look at.”

“Lighting and colour are particularly important in the built environment,” noted British interior designer Jane Priestman, a former general manager and director of architecture and design for the British Airport Authority and British Rail.

“Our research in airports and railway stations has shown that the psychological power of colour and control of lighting can influence the mood of people,” she said in a previous report.

Noise-cancelling walls

Several studies in recent years have exposed some of the detrimental effects of aircraft noise on health, including one back in 2010 which suggested that dying from a heart attack was more common among people with increased exposure to aircraft noise.

In recent times, new technology has revealed ways that aircraft noise could be reduced. Insulating the plane fuselage with a thin membrane, for example, can reduce the relentless hum of plane engines and make flying less noisy.

“We’ve also been looking at adding ‘acoustic curtains’ - padding across the plane to deaden the surrounding noises and the use of softer materials within the interior to help to deaden the sounds.

“And there's a lot of development around noise-cancelling features, both within the walls and in the individual seats near the headrests that may be used on planes in the future,” Mr Goode said.

The importance of fabric

As a general rule, most long-haul carriers won’t install leather seating because they can get unpleasantly sweaty. Synthetic fabrics breathe, which makes for a more comfortable experience.

Fabrics are chosen for their hard-wearing qualities and airlines tend to go with darker fabrics for maintenance reasons - it's much more of a bother to clear up a red wine spill on white fabric than on black, as most of us have discovered the hard way. Ergo, dark coloured seats mask dirt and therefore appear to be cleaner and longer-lasting than pale hues.

Planes often won’t use leather seating for long-haul aircraft because it can get sweaty Credit: Getty

For the same reasons, patterned fabrics are favoured over plain ones for seat covers to mask wear and tear over the years.

“Lighter-coloured interiors, however, are more commonly found in first and business class seats, given not as many people fly in those cabins as they do in economy, where you’ll see more of the darker shades," Mr Goode explains.

There’s a ‘secret’ room

Found only on wide-body aircraft like Boeing’s Dreamliner, there is a small room hidden behind what looks like a small cupboard from the exterior.

Known as the 'crew rest', this tiny compartment opens up to a steep staircase that leads down to a few seats and bunk beds where crew members can sleep.

“These hidden crew areas are less than five feet high and can fit up to four people," Mr Goode states. "This space is located in the front area at the nose of the aircraft, but most passengers would not have noticed it.”

There's plenty of unused space

There are large areas on wide-body aircraft that are not used in the lower level, which have not been converted into seating areas because of the low height and lack of windows - both of which make the space too claustrophobic for passengers.

There is a small 'secret' room near the noise of the aircraft on board wide-body aircraft like Boeing's Dreamliner reserved for cabin crew

“Previously we’ve done work on the A340 for Lufthansa where there was a lower level crew area was converted for passenger use and it’s where there lavatories were placed. But the A340 is a large plane that’s not used much anymore because they’re not really economical,” Mr Goode notes.

“These smaller pockets of unused space could be suitable for cabin crew, but it’s a more complicated process convert them into passenger seats because they need to be certified, which is expensive.”

An aircraft design featuring a lower level with windows replaced by screens proposed by Zodiac Aerospace in 2015 Credit: Zodiac Aerospace

All seats need to be certified by aviation authorities, which differs depending on the route its travelling. And even after it’s certified for one aircraft, if that seat design is used on another aircraft, it will need to be re-certified.

“It’s a laborious and expensive process, which cost millions of dollars and it’s why airlines try to avoid having to redesign or change their seats too often.” Passenger seats are usually changed between seven to 10 years on average, he adds.

“Many low-cost carriers tend to go with quite standard seats, purchased directly from manufacturers, which are already certified so it’s cheaper.”

All seats must pass the 16g test

Passenger seats with dummies strapped to them are put through the 16G test, a process which involves hurtling the seat down a 'sledge' ramp at high speeds to simulate a plane crash setting. All seats are required to withstand a 16g dynamic force.

The seats are sent down the slope at various angles to look at different crash scenarios and to see which parts of the seat need to be modified for maximum safety. All fabrics are also fire-tested to make sure they are quickly extinguishable, Mr Goode explains.

Why don't Ryanair seats recline?

Airlines are always looking for ways to keep the weight of a plane down to keep fuel costs at a minimum, often at the expense of its passengers' comfort. Seats which lack a foam covering are designed instead to be thin, light and to optimise “living space” for passengers, says Goode explains.

Seats on many low-cost carriers like Ryanair don’t have a recline mechanism, which also adds to the weight, and others go as far as removing the seatback net for magazines to help reduce weight.

In terms of flooring, there isn’t much variety in the carpets and most airlines go with either nylon or woollen carpets which are the most lightweight for cabin use.

Could the glory days of smoking on board return?

While smoking has long been banned on planes, the ashtray in the plane toilet is still a legal requirement according to the US Federal Aviation Administration's list of “minimum equipment” for aircraft. But the UK's Civil Aviation Authority says there is no mention of mandatory ashtrays, only that smoking is illegal on planes.

The tobacco-stained "golden age"

“They [the ashtrays] are there in case somebody does break the law, so that at least they will have somewhere to put the cigarette out."

“I don’t think smoking on planes will ever come back, but every so often we have received design requests that include potentially offering a smoking area or cigar bar on board," Mr Goode remarks.

What does the future hold for economy class?

There are still areas in economy class which can be developed, given the limitations that many economy seat configurations currently come with, comfort being the big one.

Air New Zealand's premium economy seating

“There’s a big push at the moment for the magazine pouch to be relocated just a tiny bit higher to allow just a little bit more space," notes Mr Goode.

There are also developments which involve moving those underseat metal boxes (which house all the wires for the in-flight entertainment) into walls or the flooring instead.

An improved angle of seats, too, can create a slight cradling effect, which enables them to move back a bit instead of just reclining.

“The major trend in economy seating, which we didn’t have previously, is more choice with the launch of premium economy, where the extra cost is definitely worth that bit of extra seat width and pitch," he concludes.