The largest procurement program in the Department of Defense (DOD), the F-35 Joint Strike Fighter (JSF), also called the Lightning II, is a strike fighter aircraft being procured in different versions for the United States Air Force, Marine Corps, and Navy. The F-35 Lightning II is intended to replace a variety of existing aircraft in the Air Force, Navy, and Marine Corps, while providing the most supportable, technologically advanced, lethal, and survivable aircraft to date. The F-35 is DOD's most expensive weapon system. This book addresses F-35 program performance during 2012, including testing, technical risks, and software; manufacturing performance indicators, production results, and design changes; and acquisition and sustainment costs going forward. This book also addresses the extent to which DOD has developed an F-35 sustainment strategy and addressed potential risks related to affordability and operational readiness; and developed a reliable O&S cost estimate for the program's life cycle.