The U.S. Environmental Protection Agency (EPA) is finally moving to start regulating greenhouse gas emissions from airplane engines, one of the last frontiers after ground transportation and power plants. The EPA wants to use authority derived from the Clean Air Act (section 231(a)) to control "air pollution that causes climate change and endangers public health and welfare," but it won't be creating the new rules alone. It is seeking help from the International Civil Aviation Organization (ICAO), which is a bit worrying because this organization is more or less run by the airline industry. I hope that they will ask for expert advice, but keep their independence and feel free to do things that the ICAO wouldn't like for the sake of our planet.
Besides, the transportation industry always grumbles at first when there are new rules, claiming that they are impossible to meet and will be too expensive. But after a while, we see a lot more innovation than was present before. Electric cars and plug-in hybrids probably wouldn't be developing at this rate if fuel economy standards weren't on a fairly steep ramp over the coming years, and if emission regulations weren't being tightened. We've seen a very long period of stagnation when CAFE standards plateaued in the 1980s and 1990s. And the current wave of change is with relatively mild modifications to the system. Imagine what a carbon tax would do (it can be revenue neutral, cut income taxes with the money raised)!
Right now, planes represent about 11% of emissions from the U.S. transportation sectors, but the industry is expected to continue growing rapidly (the FAA projects that fuel consumption will increase 49% from 2010 to 2035). And while there's a clear path for ground transportation to decarbonize (electricity, baby!), things are trickier for planes, so it's best to get started right now. One possible destination for the industry would be much more efficient planes that are powered by truly carbon-neutral advanced biofuels.