Examples of user fees include highway and bridge tolls, tickets on mass
transit, tickets on commercial airline flight (e.g. the $3 security fee
tack on -- in addition to taxes), park fees, paying municipal trash
collection fees (some jurisdictions build this into tax rates, others
charge a fee), water and or/sewer fees, car license fees, car registration
fees, etc. Tuitions at public colleges and community college districts are
also examples of user fees. Some schools charge kids an athletic fee.

And all these are collected on the spot, like a gas tax and none are
collected weeks later, like as proposed. The point is if the FBO has to
come back later and track down who owes which fees, it is much more
difficult than fees that are collected from the pilot on the spot (like
landing fees, tie down fees etc). It also takes more effort on the
gov't side to compute the amount of the charges, report them and mail
you the bill. If someone can tell me why the more complicated way is
better, than fine. Otherwise, I'll continue to say that the fuel tax is
far easier and cheaper to implement than user fees. If it aint broke...

-Robert