Mate of mine had the misfortune to wind up working for a bunch of bucket & spade cowboys many years ago. He told me , at the time, that the company declared a few aircraft to have a MTOW well below Manufacturer's figure. He was told by the CP, no less, that this was to avoid Air Traffic charges. However, the aircraft were regularly flown above the "declared" MTOW but never , of course, above the Certified Manufacturers MTOW. Cowboys loved topping up the difference in fuel & making it easy to go long distances without being charged for the heavier weight. But that was a long time ago when the Cranwell twerps were in charge & thought that there was still a war on ! Line blokes, grateful for a job, cheered them on. My mate left. He told the CP that there were two things he would never do; 1. Break the Law. 2. Endanger the lives of innocent pax. He felt that he was being asked to do both on a regular basis.