Supportability is the degree to which system design characteristics and planned logistics resources meet system requirements. Supportability is the capability of a total system design to support operations and readiness needs throughout the life-cycle of a system at an affordable cost. It provides a means of assessing the suitability of a total system design for a set of operational needs within the intended operations and support environment (including cost, equipment readiness, and manpower and personnel constraints). 
Supportability characteristics of the total system interrelate with the characteristics of the individual designs to provide a top-level assessment of the total system’s design. When a total system demonstrates its operational suitability and affordability, the total system element designs are generally considered complete, but most characteristics of a total system are subject to change over time. The rapid turnover in design and software technologies not only creates obsolescence through increased performance capabilities but also reduces available sources of supply and invalidates repair concepts. So the systems engineering process is used to monitor and assess changes in total system requirements that may lead to new requirements or opportunities for improvement. 
Supportability characteristics vary from program to program but a few of the most common ones are:
- Repair Cycle Time
- Mean Time Between Failure
- Mean Time to Repair
- Operational Availability (Ao)
- Life-Cycle Cost (LCC)
Effective supportability begins with the development of sustainment requirements to drive the design and development of reliable, maintainable and affordable systems through the Systems Engineering and Acquisition Process. A key product of supportability is the maintenance plan which evolves and drives all sustainment resource requirements throughout the life cycle.
Supportability in Systems Engineering
The systems engineering approach to the design of total systems and their major elements (hardware, software, and support) allows good supportability to be effectively “designed-in.” While poor supportability of a system element can be mitigated through the design of the remaining elements, it can only be improved by a change in design. Cost, equipment readiness, and manpower and personnel constraints should always be considered as part of the total system design process because of their ability to affect system supportability.