Laminar flow is among themost discussed technologies toward satisfying the ambitious goals ofmore fuel-efficient aviation. Both passive as well as active laminar flow control systems are sensitive to external influences and system failures. A sudden degradation of laminarflow immediately results in loss offlight performance. Such offdesign cases have to be considered in preliminary design synthesis for correct sizing of the aircraft. In the scope of this paper, an approach is presented that incorporates offdesign cases of laminar aircraft into preliminary design synthesis. The authors chose to use the extended-range twin-engine performance standards as a framework for deriving operational standards for aircraft with laminar technology. Different requirements for minimum offdesign performance are derived that directly impact overall aircraft design synthesis. In a case study, the sensitivities of the design synthesis toward these offdesign requirements are discussed. Design parameters such as maximum takeoff weight, block fuel, as well as the aircraft economics are used for evaluation of the different concepts.