available until expended: Provided , That none of the funds appropriated in this Act or any other Act may be used to establish reserves in the Working Capital Fund account other than for accrued annual leave and depreciation of equipment without prior approval of the Committees on Appropriations of the House of Representatives and the Senate: Provided further , That the Secretary may assess reasonable charges to State, local and tribal government employees for training services provided by the National Indian Program Training Center, other than training related to Public Law 93–638 : Provided further , That the Secretary may lease or otherwise provide space and related facilities, equipment or professional services of the National Indian Program Training Center to State, local and tribal government employees or persons or organizations engaged in cultural, educational, or recreational activities (as defined in section 3306(a) of title 40, United States Code) at the prevailing rate for similar space, facilities, equipment, or services in the vicinity of the National Indian Program Training Center: Provided further , That all funds received pursuant to the two preceding provisos shall be credited to this account, shall be available until expended, and shall be used by the Secretary for necessary expenses of the National Indian Program Training Center: Provided further , That the Secretary may enter into grants and cooperative agreements to support the Office of Natural Resource Revenue’s collection and disbursement of royalties, fees, and other mineral revenue proceeds, as authorized by law. Administrative provision There is hereby authorized for acquisition from available resources within the Working Capital Fund, aircraft which may be obtained by donation, purchase or through available excess surplus property: Provided , That existing aircraft being replaced may be sold, with proceeds derived or trade-in value used to offset the purchase price for the replacement aircraft. office of natural resources revenue For