Maximum Zero Fuel Weight
Some, and almost all commercial aircraft, have a Maximum Zero Fuel Weight, which is the maximum amount of weight of the aircraft without usable fuel. In order to determine the MZFW, you can simply extract the total amount of usable fuel on board from the aircraft weight. If, for some reason, the actual zero fuel weight is higher than the MZFW, items, other than fuel, must be reduced in order to reduce the total load. The reason why the MZFW is established is to determine the maximum weight that can be carried in the aircraft fuselage. Excessive loading could result into the wings flexing too far upward when generating sufficient lift required to keep the aircraft airborne.