Availability engineering is a research field and methodological approach dedicated to analyzing, predicting, and enhancing the operational readiness and uptime of complex systems. It investigates the factors influencing system downtime, including reliability, maintainability, and supportability, often employing quantitative models and lifecycle analysis to identify failure modes and optimize maintenance and support strategies. The significance of this field lies in ensuring that systems, particularly critical infrastructure, are functional and accessible when required, thereby maximizing performance, minimizing operational costs, and ensuring safety or mission success.