Born in , in the Kovno Governorate of the Russian Empire, Darius immigrated to the US with his family in 1907. In 1917 he joined the United States Army, after the United States entered World War I, and changed his name to Darius. He served as a telephone operator in the 149th Field Artillery Regiment, fought in France, was wounded and received the Purple Heart medal. In 1920, he returned to Lithuania and joined the Lithuanian Army, graduating from War School of Kaunas in 1921. He participated in the Klaipėda Revolt of 1923. While living in Lithuania he completed pilot training. In 1927 he returned to the United States and started working in civil aviation. He initially formed South Bend Airways in partnership with Carl G. Jordan of South Bend, Indiana. Their fleet consisted of a Pheasant H-10 and an Eaglerock Long Wing, both powered by OX-5 engines of World War I vintage. He lived for a while in the Jordan household prior to moving to Chicago.