This policy brief provides a side-by-side comparison of Sections 110 and 111(d) of the Clean Air Act and highlights the significant differences in requirements for state compliance plans under each section. The authors distinguish between U.S. Environmental Protection Agency’s (EPA) constrained role in reviewing and approving state plans to address fine particle and ozone pollution and the flexibility afforded by Section 111(d). The authors see significant opportunity for states to bring new approaches to air quality planning due to the unusual flexibility allowed under Section 111(d) of the Clean Air Act—the law underpinning the EPA’s proposed Clean Power Plan. States are not confined to the prescriptive federal requirements generally associated with state implementation plans (SIPs). Instead, states can craft their Clean Power Plan compliance plans based on state policy, and can even tailor their plans to achieve compliance more cost-effectively, meet other state public policy goals, and boost state employment and economic gains—as long as the plan meets EPA’s established greenhouse gas emissions reduction targets. The authors suggest several steps states can take to maximize reward and minimize risk when taking innovative approaches to air quality planning under Section 111(d).