As civil aircraft design matures and the viability of introducing new technological improvements diminishes, new criteria will need to be taken into account in the initial project design phase. This paper considers the overall situation and gives examples of parameters that may become more significant in future aircraft designs. These examples are taken from three different scenarios (aircraft performance, airport compatibility and public safety).The consideration of design aspects which are of a different type to traditional aeronautical engineering parameters will necessitate a change to the processes used in aircraft optimization. Methods developed and used in other disciplines will need to be combined with traditional parameters and the new broader based criteria to provide an overall assessment method. The paper concludes by suggesting a possible line of development.