Since oil and gas facilities can be in multiple states (i.e. operate at different production levels) ranging continuously from nil to full production, the availability, which measures the expected proportion of time in a single (up) state, is too restrictive for performance evaluations. The concept of production availability has then been defined in ISO 20815 as the ratio of production to a reference level (e.g. the design or contracted rate), over a specified period of time. It is notably used to verify production objectives and requirements, identify critical items, compare alternatives and help for economic optimisation. The present paper discusses the concepts of production availability (definitions, objectives), and presents a procedure to perform production availability analyses. The procedure, which is provided with several references, consists in objectives and preparation, study basis, model development, and production availability analyses. Contributions of the paper include a review of factors that have an impact on production availability (events included in the scope, system configuration, equipment and maintenance characteristics, scheduled shutdowns, operational constraints, etc.); the modelling principle (regarding state-based approach or behavioural modelling) and the use of flow capacity block diagrams (FCBD); the analysis principle (time-dependent and average computations, Monte Carlo simulations) and importance measures.