Real-time critical systems are those whose failures may cause loss of transactions/data, missions/batches, vehicles/properties, or even people/human life. Accordingly, some regulations prescribe their maximum acceptable probability of failures to range from about 10−4 to 10−10 failures per hour. Examples of such systems are the ones involving nuclear plants, aircrafts, satellites, automobiles, or traffic controls. They are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754A Standard. Those systems include, most of the time, real time critical software that must be specified, designed, implemented, validated, verified and accredited (VVA). To do that, models, specially the V-Model, are frequently adopted, together with methods and tools which perform software VVA to ensure compliance (of correctness, reliability, robustness, etc.) of software to several specific standards such as DO178-B/DO-178C (aviation) or IEC 26262 (automotive) among others.This paper presents an overview of models, methods and tools for verification, validation and accreditation of real time critical software.To do that, it: 1) discusses how models, specially the V-Model, are used to develop the software life cycle; 2) reviews several methods and tools for VVA of real time critical software available in the literature; and 3) compares such methods and tools according to compliance of software to several specific standards.It is expected to show that: 1) an early analysis at system-level of the models, methods and tools to be used to along the software life cycle is advantageous; and 2) the overview presented here promote a better understanding of what role such models, methods and tools should play to provide better and safer systems considering social-technical objectives as a whole.