Carrier liability under customs law: failure to account or unload can trigger confiscation and penalties. Persons in charge of vessels and aircraft bear carrier liabilities under the Customs Act where conveyances may be confiscated if constructed to conceal goods, used to prevent seizure, disobey stop or landing orders, unload drawback goods without permission, arrive with substantial unexplained shortages, or are used in smuggling. Separate penalties apply to persons in charge for failure to account for loaded or transhipped goods or for unloading deficiencies; penalties can be imposed for unexplained shortages and may be waived if satisfactorily accounted for by the competent officer.