The F-35 Joint Strike Fighter (JSF), also called the Lightning II, is a strike fighter airplane being procured in different versions for the Air Force, Marine Corps, and Navy. The F-35 program is DOD's largest weapon procurement program in terms of total estimated acquisition cost. Current DOD plans call for acquiring a total of 2,456 F-35s. Allies are expected to purchase hundreds of additional F-35s, and eight nations are cost-sharing partners in the program with the United States. Chapters 1 to 6 address issues and concerns with this program. The Trump Administration's FY2020 budget proposal includes a request for $1.1 billion to buy 8 F-15EX aircraft, the first procurement toward a planned initial buy of 144. As reported in chapter 7, this proposal represents a change from previous Air Force plans to procure only stealthy "fifth-generation" fighter aircraft. Chapter 8 examines the extent to which the Air Force's organisation of its F-22 fleet maximises availability of aircraft and utilisation of its F-22 fleet affects pilot air superiority training.