The operator is frequently considered as the main sources of vulnerability in command and control systems; for example, in a 2006 survey 79% of fatal accidents in aviation were attributed to “human error.” Beyond the case of command and control systems, users’ faults occur not only at use time but also during the design and development of systems. Following Avizienis et al.’s taxonomy for faults, human-made error can be characterized as the operator’s failure to deliver services while interacting with the interactive system. Non human-made errors are called natural faults and may occur during development or set the interactive system as well as its users into an error-state during its use. Focusing on interactive systems specificities, this paper presents a comprehensive description of faults covering both development and operation phases. In correspondence with this taxonomy, we present mechanisms to avoid, remove, tolerate and mitigate faults in order to design and develop what we call “perfect” interactive systems taking into account the organization, the interactive system, the environment and the people operating them. We define an interactive system as perfect when it blends multiple and diverse properties such as usability, security, user experience, dependability, learnability, resilience … We present multiple concrete examples, from aviation and other domains, of faults affecting socio-technical systems and associated fault-tolerant mechanisms.