I always have a piece of paper with me and and when I here s-th new at work , write it down for later investigation and googling process . this time my key word was gross-weight (wiki pedia):
I read a bit the wiki pages , in which this paragraph did have s-th new for me:
The authorised (or certified) weight limits are chosen by the customer/airline and they are referred to as the "purchased weights". An operator may purchase a certified weight below the maximum design weights because many of the airport operating fees are based on the aircraft AFM maximum allowable weight values. An aircraft purchase price is, typically, a function of the certified weight purchased.
