Abstract This paper demystifies active and passive fault-tolerant control systems (FTCSs) by examining the similarities and differences between these two approaches from both philosophical and practical points of view. Even though the control objectives of both approaches are the same, each method uses its own unique ways to achieve the objectives. Therefore, different approaches can lead to seemingly different results. Advantages and limitations of each method are examined through at philosophical level as well as quantitative case studies using an aircraft flight control system as a test system. A distinctive feature of this paper is that it provides an objective assessment of the two most popular fault-tolerant control system design methodologies in an unbiased and comparative setting.