In todays society the amount of connected devices are increasing. Many of these devices are in need of an interface to enable interaction with users. These devices are built for solving tasks of varying degree of difficulty and the need for user-friendly interfaces are highly relevant. Errors is one attribute that needs to be considered when creating a user interface. Therefore, this thesis project investigates how one can design and evaluate a user interface, which is used in a flight test environment, with regards to usability in terms of low error rate. Based on requirements gathered in the requirements elicitation process together with inspiration from the anchor-based subgoaling design principle, a low-fidelity and a high-fidelity prototype is created. To evaluate these prototypes user testing together with the thinking aloud technique is used. Data regarding the number of errors made by each user, if they complete a task or not and the users general thoughts of the prototypes are also gathered. The whole process of implementation and evaluation is done in an iterative manner. The results show that the users are satisfied with the interface, complete or partially complete each task, make few errors and can recover from the mistakes they make. Based on the results, a conclusion from this thesis can be drawn that by using an iterative design, creating prototypes inspired by the anchor-based subgoaling design principle and conducting user tests together with the thinking aloud technique one can create and evaluate a user interface with regards to usability in terms of low error rate.