I don’t understand the question. Are you meaning like the small ship lands on the mothership and then you control the mothership?
IF that is what you mean then you need an ENTER / EXIT. Kind of like a multiplayer combat game where the player walks up and presses E and gets in a chopper or tank or something?
But in your case you would not be triggering it with an input but likely by proximity which you can do through math or box collisions / overlaps, and then some logic to have the smaller ship land or dock with the bigger ship.