((a)) To conduct economically and efficiently the operations of the Department of Defense that are financed by at least two appropriations but whose costs cannot be immediately distributed and charged to those appropriations, there is the Army Management Fund, the Navy Management Fund, and the Air Force Management Fund, each within its respective department and under the direction of the Secretary of that department. Each such fund shall consist of a corpus of $1,000,000 and such amounts as may be appropriated thereto from time to time. An account for an operation that is to be financed by such a fund may be established only with the approval of the Secretary of Defense.

((b)) Under such regulations as the Secretary of Defense may prescribe, expenditures may be made from a management fund for material (other than for stock), personal services, and services under contract. However, obligation may not be incurred against that fund if it is not chargeable to funds available under an appropriation of the department concerned or funds of another department or agency of the Department of Defense. The fund shall be promptly reimbursed from those funds for expenditures made from it.

((c)) Notwithstanding any other provision of law, advances, by check or warrant, or reimbursements, may be made from available appropriations to a management fund on the basis of the estimated cost of a project. As adequate data becomes available, the estimated cost shall be revised and necessary adjustments made. Final adjustment shall be made with the appropriate funds for the fiscal year in which the advances or reimbursements are made. Except as otherwise provided by law, amounts advanced to management funds are available for obligation only during the fiscal year in which they are advanced.