Lambert served as a B-52 instructor pilot, and was director of battle staff for a B-52 wing. He rose from scientific analyst to division chief within the Air Force Studies and Analyses Agency at The Pentagon and worked on policy studies for major military systems, including bomber and intercontinental ballistic missile forces. He was deputy defense intelligence officer for Europe in the Defense Intelligence Agency. Lambert worked as an attaché at several international postings, serving as the air attaché and deputy chief of military assistance program, in Amman, Jordan, and as the defense attaché and chief of the Office of Defense Cooperation, Stockholm, Sweden. He was assigned to Air Force Space Command in 2001 as deputy director of the Space Analysis Division, where his duties included support for investigation of the Space Shuttle Columbia disaster.