As in previous lists, mention is here confined generally to units specifically authorized by law or established by the President by executive order under general authority vested in him. Changes in units created by heads of departments or independent establishments are excluded unless of major importance.Air Commerce Bureau, Department of Commerce. Duties transferred to Civil Aëronautics Authority by Civil Aëronautics Act of 1938 (Public Act No. 706, 75th Congress), approved June 23, 1938.Air Mail Bureau, Interstate Commerce Commission. Duties transferred to Civil Aëronautics Authority by Civil Aëronautics Act of 1938 (Public Act No. 706, 75th Congress), approved June 23, 1938.