Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Delta Air Lines Introduces Expandable Middle Seat Technology

Delta Air Lines is striving to redefine comfort in the air with its novel "expandable middle seat" technology. This new feature, set to appear later this year on Boeing 757 aircraft primarily used for domestic and shorter international flights, is designed to make the middle seat a slightly less dreaded experience. It's part of a broader cabin revamp, which includes other elements like memory foam cushions and tweaked lighting, aiming for a more contemporary cabin feel. Delta plans to roll out this new aesthetic across its fleet, progressively, suggesting a significant shift in their approach to the passenger experience as the airline approaches a major anniversary in 2025. While the jury is still out on whether these innovations are truly a game changer for the notoriously cramped middle seat, the changes reflect the increasing attention airlines are giving to passenger satisfaction in a competitive market. It remains to be seen if this approach to middle-seat comfort will resonate with passengers and become a trend across the airline industry.

Delta Air Lines is introducing a novel approach to middle seat design, integrating what they call "expandable middle seat" technology. The idea is to make the often-maligned middle seat a more appealing option by allowing passengers to increase its width by up to three inches. This adjustable feature is specifically designed for the middle seat, aiming to address a common passenger frustration.

It seems the airline's engineers are hoping that making the middle seat more accommodating will shift passenger preferences. Some preliminary studies suggest a potential for this, hinting at a possibility that passengers might actually prefer an expandable middle seat to fixed aisle or window seats, simply because of the additional personal space.

This approach is part of a wider industry trend to look towards other industries for solutions to the challenge of improving passenger comfort. It reminds me of how the automotive industry has long offered features like adjustable seating and ergonomic designs, and now we see it finding its way into airline seating.

This kind of innovation could potentially change how passengers perceive air travel. If travelers are happier and more comfortable, it could lead to higher satisfaction rates and potentially even greater loyalty to the airline. This is all connected to the fundamental notion that passenger experience heavily influences consumer behavior in air travel.

Interestingly, this initiative from Delta seems to be a reaction to the constant feedback that they get from customers that seat comfort, especially on longer flights, needs a lot of improvement. And in the context of middle seats, with their typically high occupancy rate in coach class, the opportunity for an airline to make a substantial change to the passenger experience is pretty significant.

Behind the scenes, Delta has likely partnered with a host of engineering firms to achieve this feat, focusing on the design and manufacturing complexities of an adjustable seat that can handle different weights and conditions, while still fitting into the cabin and looking good.

The question is, will other carriers follow suit? If enough airlines start using similar seat designs that enhance comfort, we might see passengers start to specifically seek out airlines that prioritize these features, and that could make a big difference in the travel marketplace.

What else is in this post?

1. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Delta Air Lines Introduces Expandable Middle Seat Technology
2. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Emirates Adds Memory Foam Cushioning to Premium Economy Seats
3. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - United Airlines Tests New Lumbar Support System Across Fleet
4. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - American Airlines Launches Wider Economy Seats on Boeing 787s
5. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Air France Implements Adjustable Headrest Design with Side Wings
6. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Singapore Airlines Debuts Space-saving Recline Mechanism
7. Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Lufthansa Rolls Out Ergonomic Seat Design with Extra Knee Room

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Emirates Adds Memory Foam Cushioning to Premium Economy Seats

Emirates is making a push to elevate its Premium Economy offering by adding memory foam cushioning to the seats. This is intended to provide a noticeable boost to passenger comfort, particularly on longer journeys. The airline is busy retrofitting its fleet, focusing on 67 Airbus A380s and 53 Boeing 777s. While the process is ongoing, it's expected to be wrapped up soon, which will give passengers more options for a more comfortable long-haul experience. The revamped Premium Economy boasts a wider cabin layout, especially on the A380, with a 2-4-2 configuration, a 13.3-inch HD screen for entertainment, and even faster WiFi. While Emirates has marketed this as a step up from standard Economy class with a softer price than Business, it remains to be seen if it truly sets a new benchmark for comfort in the sky. As passenger comfort becomes increasingly important in the airline industry's competitive landscape, such changes might influence traveler behavior and choices for upcoming trips. It's an interesting move by Emirates that aims to address the needs of passengers who are seeking a more comfortable yet affordable option for long flights.

Emirates' recent addition of memory foam cushioning to their Premium Economy seats is a fascinating development in airline seat design. The rationale behind this move seems to be rooted in the understanding that memory foam, by its nature, can distribute body weight more effectively than traditional materials, potentially minimizing pressure points during long flights. The material's ability to conform to body shape and temperature could improve comfort, especially for individuals with varying body types.

This approach reflects a growing trend within airline design to focus on ergonomics—the study of how people interact with their surroundings. It makes sense that airlines would take cues from ergonomic research, as comfortable seating can potentially reduce fatigue and contribute to greater passenger satisfaction. Preliminary research from the automotive industry suggests that memory foam seats can enhance both comfort and posture, with potential benefits for frequent travelers, and it seems reasonable to believe that this translates to air travel as well.

It appears that Emirates' decision isn't simply about enhancing passenger comfort—it's also a savvy move from a business standpoint. Studies have suggested that enhanced comfort directly impacts brand loyalty, indicating that passengers might choose an airline with more comfortable seats, even if the tickets are pricier. This is an interesting finding—does increased comfort translate to a willingness to pay more?


Further, this move aligns with emerging understanding in sleep science. If passengers can get better rest on board, thanks to a more supportive seating surface, this could have a big positive impact for both business travelers and leisure travelers on long-haul flights.

Beyond the obvious comfort aspects, there's also a chance that the memory foam could improve sound insulation in the seating area, which in turn could lead to a quieter and more peaceful travel experience. If this proves true, it's an often-overlooked aspect of the passenger experience that is quite relevant.

One might speculate that airlines that adopt such seating solutions could reduce some of their operational costs, too. The assumption is that more comfortable passengers might have fewer complaints or service requests, thus potentially improving efficiency for flight attendants and streamlining operations.

It seems that the overall landscape of airline competition is undergoing a shift, with airlines recognizing the value of prioritizing passenger comfort—a notion that might drive future profitability and growth. This strategy of attracting and retaining customers through superior comfort seems likely to have a significant effect in a competitive travel market.

Interestingly, the use of memory foam in airline seats is a reflection of the same trends that we see in other travel segments, like the hotel industry, which increasingly uses higher quality bedding to improve guest satisfaction scores. It’s as if passengers are demanding a higher level of comfort and convenience across their entire travel experience. This cross-industry trend could signal a significant change in how travelers assess the quality of their travel experience.

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - United Airlines Tests New Lumbar Support System Across Fleet

United Airlines is experimenting with a new lumbar support system across its planes, a move aimed at making flights more comfortable for passengers. This initiative is part of a broader push to update the interiors of their aircraft. This includes outfitting their narrow-body fleet with what they call a "signature interior" – that means new features like entertainment screens on each seat, and better ways to connect to the internet, as well as improved USB and power outlets. Furthermore, they're rolling out new business class seats, called Polaris, on the A321XLR planes. The challenge for United was that their existing Polaris seats couldn't fit on the smaller planes, so they had to design a new version. These new seats, like many of the recent developments in airline seating, seem to focus on making adjustments easier.

It's becoming increasingly clear that airlines are recognizing the importance of comfort in a very competitive market. It makes sense that they're taking cues from other industries that have long been focused on ergonomic design. The way airlines design seats and the overall cabin experience will likely continue to evolve based on what passengers are looking for and what they are willing to pay for. Perhaps United's efforts here will push other airlines to make similar investments in passenger comfort, leading to a more comfortable flying experience for everyone.

United Airlines is currently evaluating a novel lumbar support system across its entire fleet. The goal is straightforward: enhance passenger comfort, especially on those longer routes where backaches can be a major nuisance. They're essentially applying ergonomic design principles to the seating, something we often see in things like office chairs. It's interesting to see if they can translate those concepts to a confined and moving environment like an aircraft cabin.

As part of their larger plan, they are also upgrading many of their planes with newer interiors. This includes things like built-in entertainment screens, Bluetooth and USB charging capability - all the mod cons one might expect in a modern aircraft. However, their approach to Business Class on certain aircraft seems a little odd to me. The A321XLR, for example, is getting brand new business class seats because the existing Polaris seat design just wouldn’t work on a narrower-body plane. It seems like a lot of extra engineering for a minor change in the overall cabin structure.

Their First Class offerings are also getting a refresh, with upgraded seats on Airbus A319 planes. However, they haven't altered the overall layout, sticking to the tried-and-tested 2-2 configuration. That gives us 12 seats in total with a 37-inch seat pitch. It's all rather typical.

The Polaris business class seats have been popular for their adaptability and lumbar support – these seats are considered some of the best available in business class. So, there's some precedent for United to focus on the lumbar support and it might indicate a future trend.

United has also made some sustainability goals public with the idea of reaching zero carbon emissions by 2050. This focus on Sustainable Aviation Fuel (SAF) is another interesting angle, but it’s hardly related to seat comfort.

One key aspect to consider is how passenger behavior will be influenced. Studies show that a good seat significantly increases passenger satisfaction, and as a result, airline loyalty. It's a smart move for airlines to focus on this, as they constantly battle for customer loyalty.

We also see the crossover of design principles. The engineers behind these seats seem to be drawing on the lessons learned from the automotive industry, where ergonomic design is an old practice. The same principles might translate into the aviation environment.

Ultimately, it's the passenger who will determine the success of these features. If they are more comfortable, then presumably, United will make money on more ticket sales, higher prices for preferred seats and potentially fewer passenger complaints and service issues.

These design choices are really part of a wider trend in the airline industry where airlines are trying to differentiate themselves through better passenger experiences. It's all very competitive, and if United can use some creative engineering to get more people to book with them, it could be a great boon for their long-term success. It will be interesting to see if this approach to lumbar support becomes common in the aviation industry. It could have implications beyond the air travel space, too. The seating design, with its multiple functions, might well turn up in all sorts of other products, from office chairs to public transportation seating. It's an example of innovation crossing boundaries between industries.

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - American Airlines Launches Wider Economy Seats on Boeing 787s

American Airlines has been working on improving the passenger experience, particularly in economy class, with the introduction of wider seats on their Boeing 787 aircraft. This is a direct response to feedback from travelers who often complain about cramped conditions in standard economy. The new seat design, with a 3-3-3 configuration, provides a bit more breathing room by reducing the overall passenger density. This change is part of a broader trend among airlines to offer more comfortable seating, recognizing that passenger comfort is an increasingly important factor in a competitive market.

Along with wider seats, American has also made upgrades to their premium economy cabins. These changes are focused on amenities that are intended to enhance the overall inflight experience. It's clear that American Airlines is paying attention to the growing trend towards a more pleasant and comfortable passenger experience. Whether these efforts are truly enough to make a significant difference in passenger perceptions remains to be seen. But for those who frequently fly on American, and especially those looking to avoid the dreaded middle seat, it could mean a slightly more comfortable flight.

American Airlines has introduced wider economy seats on its Boeing 787 aircraft, a move that appears to be part of a larger trend within the airline industry to enhance passenger comfort. This decision isn't arbitrary; it's based on studies in ergonomics which show that increased seat width can positively impact traveler comfort, especially on longer journeys. It's interesting to note how airlines are now leveraging research to understand the link between seat design and passenger satisfaction.

The Boeing 787-8 Dreamliner's redesign includes a significant upgrade in business class, with new pod-style seats receiving positive reviews. The aircraft configuration reflects the industry trend, featuring 20 business class seats in a 1-2-1 layout and a total of 234 seats across different classes. The Boeing 787-9, meanwhile, features an even more diverse seating layout, including a larger business class section and 186 seats in economy. There's a growing emphasis on premium economy across both models, incorporating features like wireless connectivity, aimed at offering passengers more amenities.

American Airlines has chosen to implement Rockwell Collins MiQ seats for its premium economy sections, a design known for improved comfort that's also being used by Cathay Pacific. This choice indicates that the airline industry is actively exploring different seating options that emphasize passenger wellbeing. Interestingly, the overall economy cabin on the 787-8 adopts a 3-3-3 seat layout with a total of 143 seats, designed to enhance passenger space.

Beyond the specific seat design, it's clear that American is paying more attention to the overall travel experience, including aspects like increased legroom and standard shoulder room for economy class travelers. The general approach across the airline industry seems to be shifting towards a stronger focus on the comfort of passengers. It remains to be seen how effective these strategies are in the long run. Whether they translate into improved customer satisfaction and loyalty is a question we'll be able to answer in the coming months.


It's noteworthy that the move toward wider economy seats is not only driven by passenger comfort; it also has potential implications for the airline's operational efficiency and overall financial performance. A happier and more comfortable customer might be less likely to complain or create issues during the flight. Further, offering a greater variety of seating options with varying comfort levels is likely a strategy to better attract and retain different categories of customers, thus boosting ticket sales and generating additional revenue streams.



One aspect worth further consideration is the possible health implications of wider seating. Wider seats may not only contribute to better passenger comfort, but also positively influence circulatory health, especially during prolonged flights. This is a research area that holds potential to uncover interesting outcomes for airline passengers and the airline industry alike. The industry is undoubtedly on the cusp of a larger evolution in seat design and innovation, driven by a more comprehensive understanding of human needs and comfort in the airline setting. While the specifics of what future aircraft seating will look like are not entirely clear, it is clear that wider economy seats are a part of the larger trend and that innovation in this field will likely continue to flourish.

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Air France Implements Adjustable Headrest Design with Side Wings

Air France has introduced a new approach to headrest design, featuring adjustable side wings, on their Embraer 190 aircraft. These new seats, part of a broader cabin upgrade, also include features like leather upholstery and improved foam padding, aiming for a more comfortable and sustainable travel experience. The headrest's adjustable design with side wings gives passengers more control over how they support their neck and head, which could be especially helpful on longer flights. This move by Air France is consistent with a wider trend within the industry, where airlines are seeking to elevate the passenger experience through innovative seat designs and enhanced comfort. Whether this new headrest will have a substantial impact on passenger satisfaction is yet to be determined. However, it highlights the growing focus on improving comfort within airline cabins, and as such design trends continue to emerge, travelers may find more personalized comfort features offered on flights.

Air France has integrated a new headrest design featuring adjustable height and side wings into their Embraer 190 fleet. This approach is rooted in the idea that providing better support for the head and neck can contribute to a more comfortable and restful flight, especially for passengers on longer journeys. The adjustable nature of the headrest allows passengers to fine-tune the positioning to suit their individual needs, potentially leading to better spinal alignment and a reduction in the discomfort that many experience during air travel.

It’s interesting to see how this focus on ergonomics aligns with the overall trend of improving seat comfort in the airline industry. As more airlines focus on seat width and personal space, aspects like headrest design are likely to gain more attention, too. While headrest adjustments may seem like a minor detail, studies show that enhancing comfort in this area can significantly impact passenger satisfaction, creating a noticeable difference in the overall travel experience. The data strongly suggests that travelers are more likely to have a positive perception of their flight if they feel properly supported during the trip.

Air France's willingness to implement adjustable headrests could be seen as a direct response to customer feedback regarding comfort issues. Passengers increasingly expect a more comfortable and enjoyable flight, and airlines that pay attention to these expectations are likely to build stronger customer relationships. It's a competitive market, and the companies that differentiate themselves with a focus on passenger well-being could attract a loyal following.

Interestingly, the added side wings on the new headrests might have an impact beyond just support. There's a possibility that these wings could help reduce the level of background noise on the plane, offering a quieter and more relaxing environment for travelers.

The trends in airline seating design are also reflecting what we see in other product categories. Cars, for example, have long incorporated adjustable seating and ergonomic considerations into their designs, and it’s logical that the principles behind these designs would find their way into airline seats. This cross-pollination of design ideas is a common aspect of innovation, and we could see the concepts behind Air France's headrest designs find their way into other applications beyond the airline industry in the future.

It remains to be seen whether this focus on enhanced head support will be widely adopted across the airline industry, but the evidence suggests that it’s a direction many carriers might consider as they continue to refine the passenger experience. It's a natural progression in a market where passenger comfort is increasingly a key factor in deciding which airline someone will choose.

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Singapore Airlines Debuts Space-saving Recline Mechanism

Singapore Airlines is introducing a clever new reclining mechanism on their upcoming Boeing 787-10 aircraft, which are due to enter service between April and March of next year. This new design focuses on making the economy class experience a little more comfortable without sacrificing too much cabin space. The new planes will be fitted with 301 economy class seats.

The core idea is to let passengers recline without impacting the space of those behind them. This has always been a pain point for economy class travelers, especially on longer flights. It will be interesting to see if the airline manages to make a noticeable difference with this approach.

In addition to the new planes, Singapore Airlines plans to adapt its A380 fleet with similar new seat designs. This suggests that the airline sees this kind of innovation as a significant part of their future strategy, especially given that competition within the airline market is getting stronger and stronger.

It's a good example of an airline trying to find a balance between a comfortable passenger experience and the realities of packing as many passengers as possible into the limited space of an aircraft cabin. While it remains to be seen how much of a difference this innovation makes, it's definitely part of a larger trend within the airline industry to focus on providing more comfort on flights.

Singapore Airlines is making waves with the introduction of a new space-saving recline mechanism on some of its aircraft. This development is part of a broader industry trend where airlines are rethinking their seating designs to improve passenger comfort and possibly gain a competitive edge.

Let's delve into some of the intriguing aspects of this approach. Firstly, the recline angle itself has a big influence on how comfortable people feel, and studies have shown that a range of 30 to 45 degrees is usually ideal. The challenge with any recline feature is that it can impact the personal space of other passengers, which is a frequent source of complaints in crowded economy cabins. Singapore Airlines’ new mechanism aims to strike a balance between providing some recline while limiting the impact on those in the row behind.

Secondly, this new recline system could have some unforeseen implications on the structural integrity and weight distribution within the seat. Engineers are likely paying close attention to this factor, especially for longer flights where repeated movement and pressure could cause strain on materials. How well it holds up over time will be something to watch closely.

It's fascinating to look back at how aircraft seating has evolved over time. The seats in the very first passenger planes were rudimentary affairs—essentially just fixed benches. Through the years, comfort and ergonomic considerations have gradually been incorporated, and we are seeing these trends accelerate with the newer mechanisms like this one from Singapore Airlines.

There is a clear psychological factor at play here as well. It's been suggested that giving passengers more control over their seat position can boost their overall satisfaction with a flight. This is especially pertinent for economy-class passengers who often feel squeezed and constrained. The idea that they have at least some ability to customize their position for a bit more space could make a real difference.

However, achieving this 'space-saving' recline requires some intricate engineering. Designers must consider the durability and long-term performance of materials and ensure the mechanism fits within the aesthetic of the aircraft cabin. It's a difficult problem to solve, and one that requires expertise in both ergonomics and engineering.

Furthermore, this development signifies the increasing importance of seat comfort in the competitive landscape of air travel. Airlines are not just focusing on price and route maps anymore; they’re understanding that they need to provide a better overall experience to stand out. It's not unlikely that in the near future, seating features like this will become important considerations for people when making travel plans.

Interestingly, passenger preference studies show a strong demand for reclining seats. This indicates that airlines who invest in developing clever recline mechanisms could carve out a competitive advantage.

And let's not forget that safety regulations also play a significant role in the development of seat designs. Airlines have to adhere to strict criteria concerning how seats recline during flight, especially in situations like turbulence. This is a critical part of the design process, guaranteeing that passenger comfort is never achieved at the expense of safety.

Furthermore, how airline seating is designed often reflects cultural aspects of a region or demographic. Singapore Airlines' clientele generally experiences longer flights, and perhaps the idea of incorporating more individualized comfort through a recline function is a natural response to that travel profile.

Finally, it’s worth considering the long-term aspects of these seat design innovations. It's not a matter of a one-time design and then production. Customer feedback is essential to how these things are refined over time. Passenger feedback loops can drive iterative improvements and ensure that designs continuously evolve to accommodate the specific needs and preferences of the traveling public. We can expect to see more fine-tuning and refinements as airlines listen to their customers and attempt to make air travel a bit more comfortable for everyone.

Airline Seat Design Analysis 7 Ways Major Carriers Are Addressing Passenger Comfort in 2024 - Lufthansa Rolls Out Ergonomic Seat Design with Extra Knee Room

Lufthansa is introducing a new seat design called "Allegris" that focuses on improving comfort, particularly with more legroom. This new design, primarily for economy class, offers at least 75 cm (3 inches) of extra space, especially noticeable in the emergency exit rows where specific booking conditions apply. Passengers will also find features like adaptable headrests and improved overall seat ergonomics. The airline plans to incorporate the Allegris cabins across its entire fleet by the end of 2023, initially concentrating on longer-haul flights.

This update signifies a greater emphasis on passenger well-being, especially on those often cramped economy class seats. It's likely that Lufthansa is responding to passenger feedback about the need for more comfortable travel, especially on extended flights. However, while the comfort improvements seem welcome, we must acknowledge that airlines operate under the constraint of needing to efficiently maximize seat capacity on each plane. The new seats are built to be more durable, a factor that likely relates to the need for the seats to withstand use while minimizing their impact on fuel consumption.

The Allegris design is part of a larger revamp of the Lufthansa cabin experience, including a range of seat options across various cabin classes. With features like advanced seat selection and food options, Lufthansa aims to offer passengers a greater degree of control over their travel, reflecting a shift towards personal preferences. While it remains to be seen how these improvements will influence passenger choices and airline loyalty, this new seat design points to a broader trend in the airline industry towards offering a higher level of comfort and flexibility to compete in a highly competitive market.

Lufthansa's introduction of the "Allegris" seat design, particularly in economy class, is a compelling example of the ongoing efforts within the airline industry to improve passenger comfort. They claim to have added at least 3 inches of extra knee room in some seats, especially those located near emergency exits (though those might come with booking restrictions). The concept of ergonomics is central to this redesign, encompassing elements like adjustable headrests and a more thoughtful overall seat structure.

While the specific materials used are not yet fully known, the fact that they describe the seats as "well-padded" and "solid and heavy" leads to thoughts on potential trade-offs, namely fuel efficiency. Perhaps they're using new composite materials or a careful balance of cushioning materials to achieve this. It's interesting that the Airbus A350 version of this setup utilizes 201 economy class seats, with a few offering extra legroom. I am wondering how the placement of these seats and their use in practice influences other passengers' comfort. This entire design process undoubtedly involved a lot of data and simulations.

The rollout of Allegris across their fleet is slated for the end of 2023, with long-haul routes being prioritized. I anticipate that the performance of this new seating will be carefully monitored to see how well it performs in the context of a wide variety of body types and passengers' expectations.

The Allegris configuration includes a total of 14 different seat options across all classes, ranging from suites to economy class seats. This broad array of choices demonstrates that the passenger experience and tailoring of offerings are taking on a greater role. However, it seems Lufthansa is already planning to monetize some of the more desirable features – in late March 2025 they plan to implement fees for advance seat reservations for the Allegris business class. It seems to me that a large segment of travelers are becoming increasingly aware of what kind of seats offer the most comfort and are willing to pay a premium for those features.

The Allegris business class will be first introduced in May 2024 on new Airbus aircraft deliveries. I expect to see that experience will be extensively reviewed and compared to other business class seats in the airline industry. How they choose to incorporate these elements into their existing fleet, and how this translates into an overall upgrade to the passenger experience, is something I believe we will see a lot of research and discussions about for many months to come. Overall, Lufthansa's Allegris design offers a glimpse into the growing emphasis on passenger comfort in the airline industry and it could very well influence how future aircraft cabins are designed.