In 1920, at the age of 27, he transferred to the US Army Air Corps and trained as a balloon pilot, then subsequently as an airship pilot. From 1927 to 1929 he participated very prominently in several US national and international balloon races, most notably winning the prestigious
Gordon Bennett Cup with co-pilot
William Olmstead Eareckson in June 1928. In August 1929 he was commissioned as test pilot of the radical metal-hulled airship
ZMC-2, newly completed at
Grosse Ile, Michigan. After a successful series of evaluation flights, he flew the airship in September of that year to what was to become its sole home base at Lakehurst, New Jersey, arriving without mishap except for a small perforation in the envelope which press reports of the time claimed to be the result of a pot-shot en route from someone on the ground. Promoted to the rank of major in October 1930, he took command of the Materiel Division's Lighter-than-Air Branch at Wright Field, Ohio. In the period 1930-32, he learned to fly fixed-wing aircraft.
Explorer In the summer of 1934, Kepner took command of the joint National Geographic Society - US Army Air Corps Stratosphere Flight near Rapid City, South Dakota to make an attempt with the specially constructed balloon
Explorer on the manned balloon altitude record. On 29 July, the balloon ascended with himself and two fellow US Army Air Corp officers, Capt.
Albert W. Stevens and Capt.
Orvil A. Anderson as crew. However, the attempt nearly ended in tragedy when the balloon envelope ruptured near maximum height, sending the spherical pressurized gondola plunging earthwards. Fortunately, as the gondola reached lower altitudes, all three occupants were able to exit and safely parachute to earth shortly before it crashed. ==World War II==