; and (4) a person or entity engaged in the production, transportation, blending or storage of sustainable aviation fuel in the United States or feedstocks in the United States that could be used to produce sustainable aviation fuel. 5. Low carbon aviation fuel standard (a) Establishment of low carbon aviation fuel standard Section 211 of the Clean Air Act ( 42 U.S.C. 7545 ) is amended by adding at the end the following: (w) Low carbon aviation fuel standard (1) Definitions In this subsection: (A) Aviation fuel The term aviation fuel means fuel that is produced, sold, or dispensed in the United States, for civil or military purposes, for turbine-powered aviation. (B) Carbon intensity The term carbon intensity means the quantity of lifecycle greenhouse gas emissions per unit of fuel energy. (C) Credit exchange The term credit exchange means a central marketplace with established rules and regulations where buyers and sellers meet to conduct trades. (D) Fuel standard The term fuel standard means the low carbon fuel standard established under paragraph (2). (2) Establishment Not later than 1 year after the date of enactment of this subsection, the Administrator shall promulgate regulations to establish a low carbon fuel standard for aviation fuels that requires a reduction in carbon intensity for aviation fuels each calendar year such that by 2050, and thereafter, the average carbon intensity of all aviation fuel used annually in the United States is reduced by at least 50 percent, as compared to the average carbon intensity of all aviation fuel used in the United States in 2005. (3) Targets In promulgating regulations under paragraph (2), the Administrator shall set a target of a reduction of at least 20 percent in the average carbon intensity of all aviation fuel used annually in the United States by 2030, and of at least 50 percent by 2050, as compared to the average carbon intensity of all aviation fuel used in the United States in 2005. (4) Requirements In promulgating regulations under paragraph (2), the