The Cirrus SR20, top, occupies the same market slice as Diamond’s DA40 Star, bottom.

At the moment, general aviation’s distant horizon is not, shall we say, emblazoned with bright promise. Aircraft sales are down, owners are flying fewer hours, flight schools are dropping like flies and the feds grow ever more onerous. Yet even in this bleak landscape, flowers bloom and two of them are named Cirrus and Diamond.

Both companies have enjoyed—and continue to enjoy—remarkable if modest success in selling four-place composite aircraft that fly in the face of chronic bitching and moaning that there’s nothing new in general aviation. …