When, in the judgment of the National Mediation Board, it shall be necessary to have a permanent national board of adjustment in order to provide for the prompt and orderly settlement of disputes between said carriers by air, or any of them, and its or their employees, growing out of grievances or out of the interpretation or application of agreements between said carriers by air or any of them, and any class or classes of its or their employees, covering rates of pay, rules, or working conditions, the National Mediation Board is empowered and directed, by its order duly made, published, and served, to direct the said carriers by air and such labor organizations of their employees, national in scope, as have been or may be recognized in accordance with the provisions of this chapter, to select and designate four representatives who shall constitute a board which shall be known as the “National Air Transport Adjustment Board.” Two members of said National Air Transport Adjustment Board shall be selected by said carriers by air and two members by the said labor organizations of the employees, within thirty days after the date of the order of the National Mediation Board, in the manner and by the procedure prescribed by for the selection and designation of members of the National Railroad Adjustment Board. The National Air Transport Adjustment Board shall meet within forty days after the date of the order of the National Mediation Board directing the selection and designation of its members and shall organize and adopt rules for conducting its proceedings, in the manner prescribed in . Vacancies in membership or office shall be filled, members shall be appointed in case of failure of the carriers or of labor organizations of the employees to select and designate representatives, members of the National Air Transport Adjustment Board shall be compensated, hearings shall be held, findings and awards made, stated, served, and enforced, and the number and compensation of any necessary assistants shall be determined and the compensation of such employees shall be paid, all in the same manner and to the same extent as provided with reference to the National Railroad Adjustment Board by . The powers and duties prescribed and established by the provisions of with reference to the National Railroad Adjustment Board and the several divisions thereof are conferred upon and shall be exercised and performed in like manner and to the same extent by the said National Air Transport Adjustment Board, not exceeding, however, the jurisdiction conferred upon said National Air Transport Adjustment Board by the provisions of this subchapter. From and after the organization of the National Air Transport Adjustment Board, if any system, group, or regional board of adjustment established by any carrier or carriers by air and any class or classes of its or their employees is not satisfactory to either party thereto, the said party, upon ninety days’ notice to the other party, may elect to come under the jurisdiction of the National Air Transport Adjustment Board.section 153 of this titlesection 153 of this titlesection 153 of this titlesection 153 of this title