The research phase starts with an extensive literature study. To this end, a research question was drawn up, which reads as follows: What possibilities does Additive Manufacturing (AM) offer in airworthy aircraft part production and in what way can suitable parts be selected and redesigned? The most interesting findings from this literature study are as follows. The 3 most frequently mentioned benefits that AM offers the aviation industry is the ability to produce complex geometry, lightweight part production and reduce material waste. Moreover, each conserved kg saves US$3000 on an annual basis in fuel. Designated certification standards or criteria applicable for AM parts do not exist yet. Besides, material plays an overwhelming role in the selection of an AM machine. The current use in the studied literature were mainly certified metal AM parts, all were critical components from the engine or wing. Last, the production of plastic tooling is low-hanging fruit, which means that all the benefits that AM offers can also be used here and no certification is required. The result from the literature study was very educational and broad. However, not all found can be used immediately for KLM’s purpose. As a result, in the continuation of the project are some topics which were not applicable, re-examined and elaborated for KLM’s use. This involved firstly investigating the European regulatory bodies, EASA. Indeed, there are no standards or regulations for the use of AM in aviation yet. However, we know that 3D printed and certified exists. EASA explains the importance of repeatability of the production process and traceability of the material quality is the most important in general for production in the aviation. When we talk about producing and certifying parts, the certificates DOA and POA of EASA are of importance. With a DOA, an organization is allowed to design new parts within a specific category. While a POA allows an organization to produce new parts within a specific category. KLM holds of a DOA in aircraft cabin parts, but doesn’t hold a POA yet. Next are the applicable benefits AM offer applicable for KLM researched. This resulted in the top 5 of faster lead time, integrating assemblies, reducing weight, customization and reducing purchase costs. In the same way is the current use of AM by direct competitors of KLM investigated. Interesting to see that all these parts were plastic while most examples in the literature were about metal parts. With this outcome and the area in which KLM is allowed to design with its DOA is the cabin. An investigation has been done into which plastic printers may actually be used in the aviation industry to produce certified parts, due to the fact the cabin mainly consists of plastic parts. The result was only SLS and FDM. Because these 2 processes only have material that meets the general cabin material requirements applicable in the aviation. Thereafter, a list of suitable components for AM was drawn up at 3 different times with different techniques executed during these moments. In addition is a very elaborated trade-off table constructed to select part with the largest potential for each of the prior found top 5 benefits AM offers KLM. The list of criteria of the trade-off table is based on previous AM benefit consequence relations found. All criteria are rated by 8 KLM experts to provide objective weights. This resulted into the selection of 5 products for each benefit. The design phase When entering the design phase with the 5 selected products, it was realized that some of the selected were categories instead of specific products. A new route has been created for this to easily find partner numbers for each category and compile real parts. AM benefit = Selected component Faster lead time = Zodiac seat armrest Integrating assemblies* = Toilet paper holder* Reduce weight = Recaro bi-fold seat tables Customization = Boeing window shades Reduce purchase costs = Zodiac business class cabin bumpers Next is a standard template created which serves during the redesign process of each part and ensures structure but also that every concept is equally worked out. The template consists determining 4 comparison aspects, mind mapping, inspiration collage, idea sketching, CAD modeling, strength analysis and test on printability. The 4 comparison aspects create an overview on purchase price, lead time, weight and amount of parts between the original and redesigned parts. This overview easily displays whether an improvement or deterioration has been achieved with the redesign. The purchase price and weight are determined with a constructed formula. These formulas have been drawn up based on the ratio method. The lead time with an assumption, while the amount of parts can easily be counted in the CAD model. After this step is every redesign tested for strength with FEM analysis. This is done based on specific maximum use scenarios created for each component. The forces in these scenarios are determined by DINED, anthropometric database created by TU Delft. The strength analysis is highly important to validate and accept the determined comparison aspects for the redesigned parts. It can be shared that all components have passed the strength analysis. Similarly is testing on printability of a part very important. Even though all parts will be redesigned for AM, there may still be reasons why a component is not suitable for printing. It is best to remove these parts as quickly as possible. A method has been devised for this. Printability is related to 2 conditions, the function requi¬rements of the component and printer specifi¬cations. A list of function requirements are set up and linked to printer specifications of both FDM and SLS. When selecting the function requirements for the part, the limitations of the AM process will immediately be discovered which will serve to decide whether the part fits for AM or not. All 5 parts have been developed into concepts where according to determinations very large improvements have been made compared to the original part. The main target during development of the 5 concepts was the AM benefit this part was selected for. While other advantages of AM are side concerns. One thing is certain, there can be lots gained even with the side issues. Using the elaborate trade-off table constructed previously for selecting the most pro¬missing part to further develop. This resulted in the selection of the Zodiac seat armrest. The final phase During the final phase is the seat armrest redesigned concept further optimized. A specific list of requirements has been constructed and fined tuned by KLM experts specialized in airworthiness and seats. Consequently is the AM process and material selected, with which the strength analysis of the optimized component has been carried out. The process is SLS and material is PA2241FR. The maximum usage scenario has been changed to an extreme scenario where the size of the prior force exerted on the component in the concept phase is doubled for the final phase. The optimized component even passed this analysis. After this the printability test was performed for SLS and are the 4 comparison aspects determined. Next is the component is checked on its precision of dimensions and real fit on the assembly by producing tangible prototypes. Iterating the design in the real world and real use of context resulted into finalizing the CAD model. With the final redesigned armrest being pro¬duced in the eventual real specifications, could this SLS printed part be used to validate the previously determined comparison aspects with the eventual real aspects. This results in 97% reduction in lead time, 37% reduction in purchase costs and 58% in weight reduction when compared with the original part. This shows that the main benefit, lead time, the armrest is selected for is achieved. Besides, in case all current armrest will be replaced on the 777 and 787 fleet by the final seat armrest redesign, will result in a po¬tential fuel cost reduction of $4.665.000 on an annual base. After all the previous steps in design, test and maturation in the process, we have now fully completed the development of the new part and printability has been proven. The last final step is making a statement on meeting previously set requirements and whether this part has a chance of obtaining a certification. This certification should declare the part being airworthy and therefore authorized to fly. To be able to make a substantiated statement, 7 experts actively on this topic were consulted. All have been shown the list of requirements and has the issue whether or not having a chance of success at KLM and obtaining certification for this redesign has been asked. We can conclude from the conversations and discussions held. That the results together prove the armrest meet previously set requirements and provide enough confidence to conclude that the new armrest will get certified and thus succeeded. The most important thing is that the operator (KLM) accepts the new part and expiry of the ETSO certificate. And the component must be proven for flammability and the moment of breaking will have sharp edges. We know that this has happened before, which generates sufficient confidence. All in all, the results from the discussions held with 7 experts together with the real comparison aspects of the SLS printed part shows that the project has led to an amazing and successful result.