He attained ace status when he shot down three enemy observation balloons and three enemy planes. He shared his first victory, a balloon on 12 August 1918, with Charles Lefevre while with Escadrille 96. His remaining five victories were scored between 10 and 30 October 1918 while flying with the 22nd Aero Squadron. Vernam was shot down behind German lines on October 30, 1918, aged 22, later dying from his wounds. He is buried in the St. Mihiel American Cemetery in France.