"MR" == Mike Rapoport writes:
MR While the states should keep their promises, aviation would
MR still be subsidized. Aviation has a very small number of
MR participants exclusively using a large amount of
MR infrastructure. I am not saying that this subsidy is good or
MR bad but I am merely asserting that it exists.

The subsidy surely does exist, and it's huge. As I recall from
discussions about our local airport:

- The FAA, from the Federal Airport Improvement Program, will pay 90%
of the costs for airport improvement (runway widening or extension or
resurfacing, taxiways, aprons, and so forth). There's no way that the
Feds' AIP is paid completely by aviation related taxes.

- The remaining 10% must come from local or state. Here in California
there is a state airport department (part of the state DOT), and sure
enough the funds they collect get stolen most years to the General
Fund. But at most they would pay for 10%.

- Then the airport owner is usually required to kick in 1% to 2% so
the state doesn't pay the full 10%. In our case the Univ. of
California owns our airport, and they get airport money not from
taxes, but from hangar rentals and gasoline sales. I don't know
whether the airport is a source or sink of money for the UC.

GA is highly subsidized in the US, and like Mike I won't comment
further if that's good or bad.