Gus was aboard the president's train as it steamed out of Union Station in Washington, D.C., at seven o'clock in the evening on Wednesday, September 3. Wilson was dressed in a blue blazer, white pants, and a straw boater. His wife, Edith, went with him, as did Cary Travers Grayson, his personal physician. Also aboard were twenty-one newspaper reporters including Rosa Hellman.
(Ken Follett, Fall of Giants)
Bas Aarts says prepositions can be alone without their complements. And I can imagine ‘aboard’ as a preposition without complement, for there's no dictionary that calls aboard adjective. But can ‘aboard’ substitute ‘on board’ below?
Have the passengers gone on board yet? -> Have the passengers gone aboard yet?
