10 CFR § 871.1 - National security exemption.
(a) The following DOE air shipments of plutonium are considered as being made for the purposes of national security within the meaning of section 502(2) of Public Law 94-187:
(1) Shipments made in support of the development, production, testing, sampling, maintenance, repair, modification, or retirement of atomic weapons or devices;
(2) Shipments made pursuant to international agreements for cooperation for mutual defense purposes; and
(3) Shipments necessary to respond to an emergency situation involving a possible threat to the national security.
(b) The Deputy Administrator for Defense Programs may authorize air shipments falling within paragraph (a)(1) of this section, on a case-by-case basis: Provided, That the Deputy Administrator for Defense Programs determines that such shipment is required to be made by aircraft either because:
(1) The delay resulting from using ground transportation methods would have serious adverse impact upon a national security requirement;
(2) Safeguards or safety considerations dictate the use of air transportation;
(3) The nature of the item to be shipped necessitates the use of air transportation in order to avoid possible damage which may be expected from other available transportation environments; or
(4) The nature of the item being shipped necessitates rapid shipment by air in order to preserve the chemical, physical, or isotopic properties of the item.