I think this question is about the game mechanics, not in-character knowledge.
If a passenger is in a ship, the passenger is an NPC or a player that has been inactive, is there any way to make the passenger leave the ship? asking an arrest-able faction to arrest the passenger then bring it out of the ship?
The Kick Passenger button should only work if you're on a planet. It'll place the character on the square below your ship if they're able to disembark to that spot. If not, it should throw an error. How the kick passenger function works is documented in the rules on this page.