In 2019, the International Civil Aviation Organization adopted a standard for non-volatile particulate matter (nvPM) emissions from aircraft engines that included significant U.S. participation by the FAA and the Environmental Protection Agency (EPA). Under the Clean Air Act, the FAA will have the responsibility to enforce the standard at the time of aircraft certification. This rulemaking would adopt the necessary regulations for the FAA to enforce the standard in the United States. Non-volatile Particulate matter (nvPM) emissions from aircraft gas turbine engines are known to adversely impact both health and climate. The proposed new particulate matter standard for aircraft gas turbine engines is an important development that will provide a regulatory mechanism to reduce aircraft nvPM emissions and associated impacts. This new standard is a critical milestone that contributes to the US’s strategic objective to minimize the adverse environmental effects of civil aviation activities. Accordingly, the EPA and FAA share the authority for adoption, and each agency will be promulgating regulations that will together satisfy the United States’ obligation under the Chicago Convention.