Harmon attempted to land on the property of his father-in-law E.C. Benedict but could not locate it in the fading light of the day, instead landing nearby. On landing he hit a patch of rough grass which broke the chassis of the airplane. For the flight, Harmon was awarded the Doubleday-Page Trophy. Harmon and Glenn Curtiss, 1910 In September 1910 Harmon won the Harvard Cup at the Boston Aviation Meet; he competed in a bomb-throwing target contest and other events as an amateur aviator. He also was involved in another wreck of his Farman biplane but again was not seriously injured. In October 1910 Harmon participated in an aviation demonstration with Claude Grahame-White in Washington DC; later in October Harmon also set an unofficial altitude record of 24,200 ft in a balloon.

In May 1911 Harmon went to Europe to arrange for American aviators to participate in an International Aviation Meet at Belmont Park; in July he participated in a balloon race from Kansas City, Missouri, to qualify for Gordon Bennett Cup race but was forced from race when his balloon was caught in a severe thunderstorm. In December 1911 he announced retirement from balloon racing and airplanes at the behest of his wife, father-in-law, and various business associates.

Harmon returned to flight in November 1913 while spending time in England, participating in a flight from London to Paris with Claude Grahame-White. In April 1915 he, along with several other aviators and wealthy friends, participated in a scheme to commute regularly from New York to points at the eastern end of Long Island by airplane.