It's no secret that aircraft contribute to harmful emissions like road-going vehicles, and the Environmental Protection Agency is one step closer to keeping that pollution in check. It recently finalized findings showing that some aircraft produce air pollution that contributes directly to climate change. As a result, the EPA is now free to set standards for aircraft emissions that help the US honor the Clean Air Act and, ultimately, its commitment to the Paris climate change agreement. While the US is already backing an international standard, this gives it the chance to demand tougher (or at least, more America-specific) requirements.
While the EPA is some distance off from defining its emissions targets, you shouldn't expect a surge of electric aircraft as a result. As with the international standard, this is more about encouraging the development of slightly more efficient aircraft (such as the Airbus A350 and Boeing 787) than ushering in a complete revolution. Even so, that airplane makers will have to worry about US standards is important by itself -- it could lead to lighter, sleeker aircraft with engines that are geared more toward eco-friendliness than raw power.