There is a clear risk that system aspects and flight control issues are not dealt with satisfactory in the preliminary design phase. There are several reasons for this. The first is that aircraft are becoming increasingly complex and the second is that there are limited resources available at the preliminary design stage. Therefore it is a risk that preliminary design is handed over that requires a lot more attention in the system and control areas than would otherwise been needed if these matter could have been dealt with more efficiently at the preliminary design phase.With the advent of powerful simulation techniques the resources needed to do this are becoming available. There is, however, a need for tools that can be used to connect the different disciplines with each other. At present designers in different disciplines usually relays, not only on totally different tools, but also different paradigms. The research at Linköping University has been focused to bridge this gap, and to acknowledge the inherently multidisciplinary nature of aircraft design.