This discussion prompted me to look at the financial reports for the Metropolitan Airports Commission where I live. (MSP)
MAC Financials .
It seems from this that the state and local government subsidy for this airport (not mentioned in the financial reports) is the tax and rent free ownership of a few square miles of prime land, plus the ability to issue tax-exempt debt. The airport commission also has taxing power but haven't used it since 1969 according to their report. They report that their cost to airlines per enplanement is consistently below national averages - $6.04 vs $7.34 in 2009 - total enplaned passengers in 2011 was about 12 million.
If this Airport Commission had to pay real estate taxes they would be seriously broke in a month or so.
Thus, privatizing - without the tax-free land rights attached -- would be politically impossible
In Minnesota, freight railroads have to pay real estate taxes (since the late 50's early 60's)
The login to the site for the MAC financials forbids to quote any of their reports in part, only in full - so I won't
But in summary the major sources of revenue for this particular airports commission are Parking, Landing Fees, Terminal Rent, other Rent, Car Rental fees and Food and Beverage, in that order. Enough to let them maintain and improve the property.
Owning more than a thousand acres tax-free is off-the-books. (as it was for all railroads here in Minnesota up until late 50's early 60's - if I remember my 6th grade Civics class correctly - no real estate tax for railroads back then) Never mind the huge land grants 150 years ago that enabled the western US railroads to be built.
Just wondering - does the Airports Commission also own the mineral rights? The western US railroads did - witness the spinoffs back in the early days of deregulation. Burlington Northern spun off its timber interests (Plum Creek) and oil and gas interests (forget the name).
Southern Pacific famously spun off SPRINT - .
Any how when - if - air travel becomes too expensive to support - as it already is at so many small-town federally subsidized airports - will we see land sales? Mineral rights sales?
Trying to envision the evolution of various transport modes based on the history - a hundred years ago if a small town had no rail - it turned into a ghost town. Now, if a small city loses its airport subsidy, no big problem - there's still the (subsidized) roads.
Sorry if this is too rambling - trying to figure what might happen with various fuel-price and local government budget constraints.