The small airplane is too dirty for an environmentally threatened world. Thats not the view from eco-activists, but from some of the leading lights in general aviation—the category encompassing small planes such as Cessnas flown by citizen pilots. At some point, some environmental group is going to figure out that small aircraft fly leaded fuel, said Mark Moore, NASAs personal air vehicle program manager, to a meeting of engineers, aviation advocates and a billionaire corporate titan with his own private jet. Their goal, however, is not to bury private aviation, but to remake it as the greenest form of personal transit.