The noise policies of FAA and DOD all were developed in the early 1970's and earlier. Most agencies now have established their policies after 1995. There is evidence that exists that aircraft noise is more annoying than road traffic at the same DNL level. For residential areas and other noise sensitive land uses, noise pollution becomes significant in urban areas when the DNL exceeds 55 decibels. In suburban areas where the population density is greater, noise pollution toleration is less. The DNL tolerance in rural areas is down to 45 decibels (Schomer and Associates, 2001). .
Other issues that are affected by aircraft noise are real estate values, land use, wildlife, and farm animals (Richards, 1973). When it comes to over flights over sensitive lands such as national parks, the National Park Conservation Association (NPCA) becomes very defensive on the issue. The NPCA battles against commercial air tours over national parks continuously. The FAA has presented at least seven proposals to expand or construct major airports near national parks across the United States. Because of the NPCA's efforts to change legislation, the FAA is required to cooperate with the Park Service in developing management plans in parks where over flights could occur (Mackay, 1999). .
One of the popular stories taken straight from an article from the NPCA's website is on a development of the FAA's that would threaten the local habitats and increase the noise pollution in that area. The proposal involves Hawaii's Kahului Airport. Including noise pollution and development, non-native plants and insects, reptiles, and viruses were examples of species carried by international planes that have come into the island's biodiversity. More native species have been driven to extinction on Hawaiian islands than in any other state in the United States (Mackay, 1999).
Another expansion proposal occurred at the St. George Municipal Airport, Utah.