The subject of this thesis report is a new concept design recommendation for Zodiac Aerospace with respect to better hygiene and cleanliness in aircraft lavatories during long haul flights.An integrated design research approach is taken to solve the issue of poor hygienic behaviour in the lavatory. This includes an analysis of the current standards and practices surrounding aircraft lavatories, a review of existing products, an analysis of relevant stakeholders, observational research onboard active flights and finally a concept design which aims to improve passenger hygiene. Research indicates that the small form factor of the lavatory makes it challenging for passengers to behave in a hygienic manner. The new design emulates the cubicle based layout of public restrooms, where wash basins are shared. Each lavatory increases in size by removing their wash basins and situating them in the cabin, where they are shared by passengers. Provision of separate lavatories for men and women enables the use of urinals for men and additional space for women and passengers with reduced mobility. Aircraft lavatories can be kept clean on long haul flights by creating new lavatory services and layouts which expand the space within the lavatory. Airlines can improve passenger hygiene and therefore satisfaction by providing lavatories which are larger and cater to more specific needs, such as standing and sitting urination. The new design is also of benefit to the process of manufacture and maintenance as it simplifies the existing product significantly and reduces the time it takes to clean and disinfect the aircraft between flights.