Pursuant to a congressional request, GAO provided information on airport-related noise, focusing on the: (1) types of projects that are eligible for federally authorized funding to reduce airport-related noise or mitigate its effects; (2) differences in the major methods for measuring the impact of airport-related noise; (3) Federal Aviation Administration's (FAA) noise standards for civil subsonic turbojets and the reasons some of those aircraft are not required to comply with these or earlier standards; and (4) status of FAA's Land Use Planning Initiative and the major issues the initiative has raised about how best to address airport-related noise.

GAO noted that: (1) most projects that reduce airport-related noise or mitigate its impact are eligible for federally authorized funding; (2) to be considered for funding under the Airport Improvement Program (AIP), a project must be part of a FAA-approved noise compatibility program; (3) in selecting which noise-related projects to fund, FAA gives priority to projects affecting communities exposed to noise levels of 65 decibels or higher, as determined by FAA's chosen measurement method; (4) in contrast to projects funded by AIP, projects funded by the Passenger Facility Charge program do not have to be part of a noise compatibility program; (5) since the programs began, 75 percent of the grants and over 50 percent of the passenger fees approved for noise-related projects have been used to acquire land and soundproof homes and other buildings; (6) the three principal methods for measuring community exposure are mathematical calculations that differ in the impact each places on noise from flights that occur during different times of the day: (a) one method treats the impact of all flights equally whenever they occur; (b) the second method differs from the first by assigning greater impact to the noise from each flight that occurs during the nighttime than to flights that occur during other times; and (c) the third method assigns additional impact to evening flights as well as nighttime flights; (7) noise standards for regulating aircraft noise from civil subsonic turbojets are generally based on an aircraft's weight and number of engines; (8) the heavier the aircraft and the greater the number of engines, the more noise the aircraft is allowed to generate and still comply with the required noise limits; (9) the newest set of standards--stage 3 standards--apply to all aircraft weighing more than 75,000 pounds and to newly manufactured aircraft weighing 75,000 pounds or less; (10) these lighter aircraft did not have to be retired under earlier noise standards because FAA concluded that it was questionable whether the technology existed to modify those aircraft in a cost-effective manner; (11) under its Initiative, FAA announced five short-term actions in May 1999 designed primarily to provide information that state and local governments can use to improve the compatibility of land uses near airports; and (12) based on comments provided by the aviation sector and the general public, there are four principal areas of concern associated with the Initiative.