Sentence:  There is an hour or two, after the passengers have embarked, which is disquieting and fussy. Mail bags, so I understand, are being put <WSD>on board</WSD>. Stewards, carrying cabin trunks, swarm in the corridors. Passengers wander restlessly about or hurry, with futile energy, from place to place. 
Meaning of the word marked with <WSD> tags:  On or in a means of transportation.