The Secretary of Transportation is authorized and directed to consider the application of any citizen of the United States for financial aid in the operation of a vessel or vessels, which are to be used in an essential service in the foreign commerce of the United States or in such service and in cruises authorized under section
1183 of this Appendix. In this subchapter VI the term “essential service” means the operation of a vessel on a service, route, or line described in section
1121
(a) of this Appendix or in bulk cargo carrying service described in section
1121
(b) of this Appendix. No such application shall be approved by the Secretary of Transportation unless he determines that