The Lockheed Martin F-35 Lightning II incorporates many significant technological enhancements derived from predecessor development programs. The X-35 concept demonstrator program incorporated some that were deemed critical to establish the technical credibility and readiness to enter the System Development and Demonstration (SDD) program. Key among them were the elements of the F-35B short takeoff and vertical landing propulsion system using the revolutionary shaft-driven LiftFan® system. However, due to X-35 schedule constraints and technical risks, the incorporation of some technologies was deferred to the SDD program. This paper provides insight into several of the key air vehicle and propulsion systems technologies selected for incorporation into the F-35. It describes the transition from several highly successful technology development projects to their incorporation into the production aircraft.