We outline a benchmark carbon dioxide (CO₂) intensity system with tradable permits for the aviation industry that will incent in-sector emission abatement opportunities that cost less than the social cost of carbon (SCC). The system sets benchmark emission intensities (CO₂ emissions per revenue ton kilometer) by route group and facilitates flexibility in meeting the benchmarks by allowing airlines to sell permits if they operate more efficiently than the benchmarks, and buy permits if they do not meet the benchmarks. The CO₂ benchmark system could operate concurrently with existing measures to mitigate aviation CO₂ emissions, will reduce the number of offsets needed to achieve carbon-neutral growth, and provide another (optional) lever to address fairness issues in climate regulations. Moreover, by providing a blueprint for other industries to price marginal emissions at the SCC, a CO₂ benchmark system could preserve the ‘carbon budget’ for use by high-cost abatement industries such as the aviation industry.