EXECUTIVE SUMMARY  Aviation Emissions and Air Quality Handbook  The long-standing relationship between aviation and air quality continues  to endure as the aviation  industry seeks to (i) develop, expand,  and/or improve its facilities , equipment, and procedures ; (ii)  repair/replace aging infrastructure; and/or (iii) accommodate the forecasted growth in air traffic; while  implementing sustainable practices. Meanwhile, air quality regulatory agencies continually strive safeguard human health and the natural environment from the effects of air pollution  – including the air  emissions associated with aviation.  In support of this relationship, t his  Aviation Emissions and Air Quality Handbook  (the  Handbook ) has  been published by the Federal Aviation Administration (FAA) as a tool and resource to assist  in the  planning and completion of  air quality assessments$^{1}$conducted for aviation-related projects and/or actions.  More specifically, the purpose of this  Handbook  is essentially three-fold:  • To provide guidance, procedures,  and methodologies appropriate for use in carrying out quality assessments prepared in association with FAA-supported projects/actions;  • To help ensure that these air quality assessments meet the requirements of  the National  Environmental Policy Act (NEPA), the federal Clean Air Act (CAA), and other relevant laws and  regulations; and  • To provide a process for users to determine when an air quality assessment is considered  necessary, the type of analysis that is appropriate, and the level of effort that is warranted.  Notably, this  Handbook  was prepared for use by the FAA, its  lines of business, and offices as well as  airport sponsors and/or their representatives that are involved in the assessment of air quality impacts  associated with aviation -related projects/actions. However, it is intended that other stakeholders will  likewise find it useful including federal/state/local governmental agencies and others with an interest in  ensuring that the nation’s airports are continually modernized while safeguarding air quality.  By  necessity, the  Handbook  is also designed to be used by both seasoned practitioners and newcomers to the  aviation air quality assessment process.  The earliest version of the  Handbook  was published in 1982 by the FAA and the U.S.  Air Force, was  fully revised in 1997, and subsequently updated by  Addendum  in 2004. While some of the materials  contained in these earlier versions are reused, it is intended that this version of the  Handbook  replace and  supersede these documents. As of the publication of this version of the  Handbook , previous versions are  cancelled. Moreover, as a guidance document, the  Handbook  is not intended to replace laws, regulations,  or other requirements pertaining to air quality. This  is a guidance document and should not be  cited as the source for legal requirements. In the case of any discrepancies or differences found between  the laws/regulations and the  Handbook , users should defer to the specific language and requirements  contained in the laws/regulations.  Finally, the contents of the  Handbook  are organized around a framework of topics and sections that build  upon one another in a progressive fashion. However, for those that wish to focus on particular topics of  interest, each section is designed to be self -supporting and comprehensive. To aid in the  understanding  and use of this material, a set of Appendices are also provided that present detailed "how to" instructions,  examples and further explanation.  For general questions regarding this  Handbook  contact the FAA Office of Environment and Energy  (AEE), Emissions Division.  For the purpose of this  Handbook  an air quality assessment encompasses both the qualitative and the technical aspects of  assessing air quality such as performing air emissions inventories, dispersion modeling, etc., as well as determining whether  compliance with the CAA, NEPA, and if applicable, other state and local air regulations is achieved.  1  i 