This action proposes Federal Implementation Plan (FIP) requirements to address twenty-six states’ obligations to eliminate significant contribution to nonattainment, or interference with maintenance, of the 2015 ozone National Ambient Air Quality Standard (NAAQS) in other states. The U.S. Environmental Protection Agency (EPA) is proposing this action under the “good neighbor” or “interstate transport” provision of the Clean Air Act (CAA or Act). The Agency proposes establishing nitrogen oxides emissions budgets requiring fossil fuel-fired power plants in 25 states to participate in an allowance-based ozone season trading program beginning in 2023. The Agency is also proposing to establish nitrogen oxides emissions limitations applicable to certain other industrial stationary sources in 23 states with an earliest possible compliance date of 2026. These industrial source types are: Reciprocating internal combustion engines in Pipeline Transportation of Natural Gas; kilns in Cement and Cement Product Manufacturing; boilers and furnaces in Iron and Steel Mills and Ferroalloy Manufacturing; furnaces in Glass and Glass Product Manufacturing; and high-emitting equipment and large boilers in Basic Chemical Manufacturing, Petroleum and Coal Products Manufacturing, and Pulp, Paper, and Paperboard Mills.