The most important factor in aircraft flight safety is the interfaces, which provide human-machine interaction. There is a close relationship between flight safety and interface usability with pilot-cockpit interaction quality. The consequences of crew errors in interacting with cockpit interfaces are catastrophic. Interaction quality and flight safety can be improved with a user-friendly interface design. Different usability evaluation techniques are applied for interface design and usability in literature. Subjectivity within most usability evaluation techniques may lead to inaccurate results. In this study, a multi-criteria approach is offered for the usability evaluation, improvement and ranking of cockpit interfaces. Alternative interfaces, used in this study, are the results of quantitative, qualitative and unified design approaches. More satisfactory results were obtained from the unified design.