 He worked at Humble Oil as an economist from 1965 to 1968 in the Corporate Planning Department.In 1968, Lay entered the Officer Candidate School for the United States Navy where, from 1968 to 1971, he rose to the rank of lieutenant and was the special assistant to the Navy Comptroller and Financial Analyst at the Office of Assistant Secretary of the Navy in the Department of the Navy at The Pentagon.Lay worked from 1971 to 1972 as a technical assistant to commissioner and vice chairman (federal energy regulator) of the Federal Power Commission and served as the energy deputy under secretary for the United States Department of Interior until 1974.