In one respect the “contest” was not a contest at all. Milling, the only other participant, had aircraft problems that kept him on the ground. The flight demonstrated one of the doctrinal missions for Army aviation, something the Army air arm was still struggling to define. Perhaps because of these circumstances, Arnold did not take himself or his accomplishment too seriously. The young lieutenant wrote that, “It [the trophy] certainly is handsome. I figure that it will hold about four gallons so I cannot see how you can fill it with anything but beer.”
He was not far off. While cleaning the Mackay Trophy one day in 2006 (it is housed at the Smithsonian National Air and Space Museum) the curatorial staff tested the volume of the trophy using non-reactive Styrofoam balls. In fact, the Mackay Trophy cup holds a volume of five gallons (of Styrofoam balls anyway).