10 U.S.C. § 8245

An aircraft flight ration chargeable to the proper Navy or Marine Corps appropriation may be furnished to members of the naval service and to civilian employees of the Department of the Navy while engaged in flight operations. The flight ration is supplementary to any ration or subsistence allowance to which the members or employees are otherwise entitled. However, the flight ration may not be furnished without charge to any person in a travel status or to any person to whom a per diem allowance is granted in place of subsistence.