Spare parts purchased or held for future use in the U.S. should be expensed, unless the spare parts are purchased for fleet maintenance and rebuild or they are held as operational standby units. Fleet spares may be capitalized as property and expensed when used unless capitalized as part of a rebuild. Operational standby units may be capitalized and depreciated over the appropriate asset life for that product line. Refurbishment and repair costs for operational standby units are expensed. In addition, only one operational standby spare may be capitalized for any one unit or assembly