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There's been a bit in the media about weighing passengers in order to get more accurate take off weights for commercial planes. I'm guessing the delta between a heavy set of passengers and a light set might be 3000 kg. If there was a cheap way of determining the weight that has been loaded onto a commercial jet would it be valuable out not, given this level of weight difference? I am after an actual cost. What is the cost of an airliner carrying the additional fuel required by current rules if it assumed the overall mass estimate is 3000kg too high throughout its life? It won't be using that fuel but it will have to carry it.