The use of maintenance cost data can be successfully employed as a design constraint for product support. This paper summarizes the process used in translating quantitative maintenance cost requirements into specific design criteria. It describes the airline operator's use of such data and how he then passes cost objectives on to the aircraft manufacturer. The various steps used in the design process are described from a manufacturer's standpoint. Examples are given to show the relationship of cost to resulting maintainability improvements. Finally, the airline operator's viewpoint is presented which calls for more stringent compliance with previously determined maintenance concepts and procedures. The paper closes with a look at future program requirements.