Originally Posted by
flyingfemme
Hence the charges are biased towards the lower end of the weight scale and the big boys pay proportionally less.
I guess that depends on your point of view. ATC has the same amount of work, regardless of whether it's a 2000 kg SEP or an A380. In fact, arguably ATC needs to spend proportionally more time with GA than with A380s, as GA generally flies slower and thus spends more time in a certain bit of airspace. However, the ATC charges are based on (the square root of) the MTOW, so the big boys pay significantly more for the same service.