The Hourly Maintenance Cost (HMC) is the main expense in running the helicopter’s major components for one hour. The HMC includes the parts and labor required for scheduled and unscheduled maintenance and scheduled inspections which are accomplished at twenty-five flight hours or greater. Each HMC does not include the labor charges for routine inspections and servicing that are accomplished at intervals of less than twenty-five flight hours. HMCs are determined by computing the cost of each major-cost overhaul and retirement item, with its associated labor costs, then dividing that sum by its allowable flight hours. The resulting per-hour costs are then totaled. HMCs are given as a range of costs due to different parts costs, varied transportation and labor charges, discounts, and above- or below-average labor time. We then add an average dollar "shop rate" for labor to remove and replace parts, and compute the internal employee costs for all other labor. If an operator does not employ in-house Certificated maintenance technicians, that operator's HMC will likely be higher. An operator with complete in-house maintenance capabilities may find their HMCs are slightly lower than the published HMCs.