AIP funding and budget is not understood by many.
http://www.faa.gov/airports/aip/
"How Much of the Project Cost Does the Grant Cover?
For large and medium primary hub airports, the grant covers 75 percent of eligible costs (or 80 percent for noise program implementation). For small primary, reliever, and general aviation airports, the grant covers a range of 90-95 percent of eligible costs, based on statutory requirements."
"...What Types of Projects Are Eligible?
Eligible projects include those improvements related to enhancing airport safety, capacity, security, and environmental concerns. In general, sponsors can use AIP funds on most airfield capital improvements or repairs and in some specific situations, for terminals, hangars, and nonaviation development. Any professional services that are necessary for eligible projects such as planning, surveying, and design are eligible. Aviation demand at the airport must justify the projects, which must also meet Federal environmental and procurement requirements."
Increased operating costs of a larger airport are not covered by AIP, but the cost of the improvement project is usually 75% in the form of a reimburseable agreement.