As I mentioned, the landscape for some of the fees, whether they're charged at the local level or at the federal level, can be quite complex.
Let me just run through an example of some of the fees that are charged. There are government fees and taxes, rent and the air transport security cost. Rent is in recognition of the fact that an airport is operating on federal lands and is a federal asset, so there's a return to the government as a result of the use of that asset.
In terms of airport improvement fees, those would be charged more at the local level. The formula for an airport improvement fee is set at the federal level. It's there to help address where that fee could be charged.