The F-35 is the result of the Defense Department's Joint Strike Fighter (JSF) program, which sought to build a multirole fighter optimized for the air-to-ground role with secondary air-to-air capability. The JSF requirement was to meet the needs of the Air Force, Navy, Marine Corps and allies, with improved survivability, precision engagement capability, and reduced life cycle costs. By using many of the same technologies developed for the F-22, the F-35 has the opportunity to capitalize on commonality and modularity to maximize affordability.
The Lockheed Martin X-35 was chosen over the competing Boeing X-32 primarily because of Lockheed’s lift-fan STOVL design, which proved superior to the Boeing vectored-thrust approach. The lift fan, which is powered by the aircraft engine via a clutched driveshaft, was technically challenging but DoD concluded that Lockheed has the technology in hand. The lift fan has significant excess power which could be critical given the weight gain that all fighter aircraft experience.
Lockheed Martin developed four versions of the Joint Strike Fighter to fulfill the needs of the Navy, Marine Corps, Army, Air Force and the United Kingdom Royal Air Force and Navy. All versions have the same fuselage and internal weapons bay, common outer mold lines with similar structural geometries, identical wing sweeps, and comparable tail shapes. The weapons are stored in two parallel bays located aft of the main landing gear. The canopy, radar, ejection system, subsystems, and avionics are all common among all different version as is the core engine which is based on the F119 by Pratt & Whitney.