In the course of the twentieth century, military aircraft led the aerodynamic way. Well funded by government expenditures, the manufacturers of military aircraft were able to push the performance envelope farther and faster. In that same period of time, the procurement of military aircraft declined in direct relation to their growth in cost. This phenomenon gave rise to Augustine's Law, which posits that if the trend continues, an air force will be able to afford only one aircraft for all its needs. It has not quite reached that level yet, but while the United States built hundreds of thousands of military aircraft during World War II, it is now buying them at the rate of a few dozen per year. Other nations face the same problems, and aircraft are now considered a platform to carry newly developed weapons rather than as weapon systems in themselves.
This new concept of aircraft simply being a place to put new weapons has kept some types, such as the Boeing B-52 and KC-135, in service for more than 50 years. This is important in terms of economy--if you amortize a $6 million B-52 over 50years, it is an amazingly inexpensive weapon. But perhaps more important than reasons of economy or anything else, at the end of almost a solid century of warfare, the aircraft and its new generation of precision-guided munitions have assumed a vastly greater role than ever before. For the first time since 1945, an alternative method of obtaining decisive results from the air is now available with the efforts of stealth aircraft, cruise missiles, airborne command and control systems, and the use of massive satellite systems for intelligence, communication, navigation, and meteorology. These are artfully combined in combat to create incredibly accurate bombing systems that may prove to be the way out of the nuclear dilemma, for they can achieve decisive results without having to resort to dropping thermonuclear bombs. There is some irony in this, of course, because it was the airplane that enabled the use of atomic weapons in the first place.
The path from the tracks scratched in the sands of Kitty Hawk by the Wright Flyer to the footprints on the moon to the probes that have ventured out of the solar system has been long, swift, and exciting. You'll see this history etched in the images that follow.