Don't say:
He sat the passengers one by one.

Say:
He seated the passengers one by one.

Note:
Don't contuse sit with set, which usually means to place. Common idioms w/th set: to set the table, to set on fire, to set off (or out), to set a trap, to set a dock, to set a price, to set your heart on, to set free, to set an example, to set a broken bone, to set to work {= to start work). Use sit as an intransitive verb. Seat is a transitive verb and requires an object Very often the object of seat is a reflexive pronoun: He seated himself near the fire. The principal parts of the two verbs are: sit, sat, sat, and seat, seated, seated.