Therefore, companies must carefully evaluate their maintenance needs and choose the most suitable strategy that balances their goals with potential limitations and trade-offs. Overall, these operational strategies play an essential role in ensuring safe and efficient transportation, particularly in aviation. By choosing the appropriate operational strategy and combining it with proper maintenance practices, organizations can optimize their operations and minimize the risk of equipment failure, which can lead to significant financial losses and potentially catastrophic accidents. Various indicators can be used to evaluate the operation process, particularly reliability, serviceability, or efficiency. Selected ones include [13; 14]:  
* Mean time to failure (MTTF) is a reliability metric that estimates the average time that a system or a component will work correctly before failing. MTTF is often used for products with a limited lifespan, such as electronic devices or mechanical systems, to estimate how long they will last before requiring maintenance or replacement. MTTF is calculated by dividing the total time of operation by the number of failures during that time. * Mean time between failure (MTBF) is a measure of the reliability of a system or a component. MTBF is defined as the average time between two consecutive failures of a system or a component under normal operating conditions. MTBF is often used to estimate the maintenance and repair schedule for a system, as it helps to predict when the system is likely to fail. MTBF is calculated by dividing the total operating time by the number of failures. * Mean time to repair (MTTR) is a maintenance metric that measures the average time required to repair a system or a component after a failure occurs. MTTR is an important factor in determining the availability of a system, as it affects the downtime of the system. A lower MTTR indicates a quicker repair process and faster system recovery. MTTR is calculated by dividing the total repair time by the number of repairs. Overall equipment effectiveness (OEE) is a measure of the efficiency of a production system, typically used in manufacturing or other industries that use equipment. OEE measures the percentage of time that a machine or equipment is producing quality output during scheduled production time. OEE considers three factors: availability, performance, and quality. The equipment utilization rate is a component of OEE and measures the percentage of time that a machine or equipment is available for production during scheduled production time. The equipment utilization rate is calculated by dividing the total production time by the scheduled production time. OEE is a widely used general indicator in the manufacturing industry that represents three key performance factors: availability, utilization, and quality. Availability is the ratio of the time planned for the execution of a task to the time that can be spent on the task. Utilization is the ratio of available time to actual work. Quality is the ratio of good to defective products produced. Together, these factors provide a comprehensive view of a manufacturing process's performance and can help identify areas for improvement. Aviation also uses reliability metrics to assess the operational process [15]. Dedicated computerized operating support systems are used for this purpose, where data from the operational process is collected and periodically analyzed. Data collection and analysis can be applied to any purpose and technical facility, provided that the data are reliable and comprehensive. In reliability assessment, particularly important are the data on failures and defects, with all the parameters of their occurrence (i.e., the time or resource of work that the equipment has worked), and a detailed description of the symptoms, causes, and the method of repair. In these data collection systems, the most valuable data are the information on the causes of downtime, as well as the method of restoring the equipment to serviceability.