48 CFR §47.404

1. (a)Agencies may use air freight forwarders that are engaged in international air transportation (49 U.S.C. 1301(24)(c)) for U.S. Government-financed movements of property. The rule on disallowance of expenditures in 47.403-3(a) applies also to the air carriers used by these international air freight forwarders.
2. (b)Agency personnel shall inform international air freight forwarders that to facilitate prompt payments of their bills, they shall submit with their bills (1) a copy of the airway bill or manifest showing the air carriers used and (2) justification for the use of foreign-flag air carriers similar to the one shown in the clause at 52.247-63, Preference for U.S.-Flag Air Carriers.