In October 1914, Gantz transferred from the 23rd Infantry to the Aviation Section, U.S. Signal Corps, and became a pioneer aviator during the Pancho Villa Expedition, making him an early bird of aviation. On September 1, 1915, Gantz married Beatrice Wooster Miller. At the time of his engagement to Weber, Gantz was a wealthy orange rancher and the owner of the 140-acre El Dorado Ranch in Fullerton, California. Gantz is credited with bringing Weber "out of a retirement which was more nearly a despondent withdrawal from public life". However, Anthony Slide indicates that Gantz was "something of an opportunist, who persuaded Weber to marry him — and co-incidentally let him manage her considerable fortune."