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$^{1 }$Contributions of CH$_{4 }$ emissions from commercial aircraft are reported as zero. Years of scientific measurement campaigns conducted at the exhaust exit plane of commercial aircraft gas turbine engines have indicated that CH$_{4 }$emissions are consumed over the full emission flight envelope [Reference: Aircraft Emissions of Methane and Nitrous Oxide during the A lternative Aviation Fuel Experiment , Santoni et al., Environ. Sc i. Technol., July 2011, Volume 45, pp. 7075-7082]. As a result, the EPA published that: “…m ethane is no longer considered to be an emission from aircraft gas turbine engines burning Jet A at higher power settings and is, in fact, consumed in net at these higher powers.” [Reference: EPA, Recommended Best Practice for Quantifying Speciated Organic Gas Emissions from Aircraft Equipped with Turbofan, Turbojet, and Turboprop Engines , May 27, 2009 [EPA -420-R-09-901], http://www.epa.gov/otaq/aviation.htm]. In accordance with the followin statements in the 2006 IPCC Guidelines (IPCC 2006), the FAA does not calculate CH $_{4 }$emissions for either the domestic or international bunker commercial aircraft jet fuel emissions inventories. “ Methane (CH$_{4}$) may be emitted by gas turbines during idle and by older technology engines, but recent data suggest that little or no CH 4 is emitted by modern engines.” “Current scientific understanding does not allow other gases (e.g., N$_{2}$O and CH$_{4}$) to be included in calculation of cruise emissions .” (IPCC 1999). 

$^{2 }$Not all HAPs are emitted by these sources. To identify the type of HAP emitted by this source category refer to the FAA/EPA documents: Recommended Best Practice for Quantifying Speciated Organic Gas Emissions from Aircraft Equipped with Turbofan, Turbojet, and Turboprop Engines (Version 1.0), May 2009 [EPA -420-R-09- 901], http://www.epa.gov/nonroad/aviation/420r09901.pdf; and Guidance for Quantifying Speciated Organi Gas Emissions from Airport Sources, Version 1, September 2, 2009, http://www.faa.gov/regulations_policies/policy_guidance/envir_policy/media/Guidance%20for%20Quantifying% 20Speciated%20Organic%20Gas%20Emissions%20from%20Airport%20Sources.pdf. 3 

GHG emissions from these sour ces are strictly related to the “activities” of these sources, and thus considered under the stationary/area source category. 

