September 25, 1923. Brigadier General William Mitchell in Washington, D.C. An important figure in the development of military aviation, "Billy" Mitchell is regarded as the father of the U.S. Air Force. His criticism of Army and Navy leaders after the crash of the airship Shenandoah in 1925 led to a court-martial and subsequent resignation. When it came to clothes, cars and horses, he was a connoisseur of the good life.