Sometimes, you do your best and still get low on fuel. That has happened about 3 times to me, always because of performance restrictions or TOW being reached. In all cases, we have spoken to approach radar in good time, explained the situation and have always been treated very well. The last one was a long westbound flight with an enroute div planned, into 140kt headwinds ending in the desert. Weather fine, holding about 300kgs above CMR, we spoke to LA and they passed it forward, everyone knew the situation and we landed with 6 tonnes - I loaded 72 !
Communication early is the key, if you go with min fuel, and are then looking for sympathy it lays between two well known words in the dictionary ! Take it when you can, talk early when you can't
