> Even setting aside passenger weights and carry on, are you saying any time I pay for an overweight piece they literally rebalance everything and add more fuel

> Even setting aside passenger weights and carry on, are you saying any time I pay for an overweight piece they literally rebalance everything and add more fuel? Very much so, yes. After the check-in is closed, the pilots will calculate the required amount of fuel for the flight based on the number of passengers they have, and the weighted hold luggage. And although the checked-in luggage will not be placed in the hold piece by piece to rebalance the plane correctly, they are roughly distributed to not unbalance the plane too much. (Different story for smaller aircrafts, as they have much stricter weight-placement requirements).