The Joint Strike Fighter program was conceived by the Pentagon because it can afford only one major aircraft engineering and manufacturing development program between now and at least the year 2010. Being the largest military aircraft program ever planned, it has a basic requirement for three aircraft. The JSF will service the US Air Force, the US Navy and the US Marine Corps. These three services have identified what they believe are critical needs: The US Air Force needs an inexpensive fighter to maintain force structure as the F-16 is retired. The US Navy has no stealthy, deep-strike aircraft. The US Marine Corps must replace the AV-8B Harrier with an advanced STOVL aircraft. In November 1996 Lockheed Martin and Boeing were selected by the Pentagon to each build prototype aircrafts of their initial designs. Joint Strike Fighter, the flight-simulator based on these aircraft, is the first interactive game enabling PC-owners to test-fly the two new American stealth aircraft. The JSF will be used for deep-strike missions, going "down-town" against its most critical targets such as headquarters, command centers and air bases, using heavy precision-guided weapons such as the 900 kilo JDAM. The US Air Force JSFs will be used with a greater emphasis on air-to-surface missions than today’s F-16s. The JSF is likely to take on the suppression of enemy air defense. Once air supremacy has been established, JSFs will become the asset of choice against many mobile targets. The JSF will also be the most likely aircraft to protect airlifters from SAMs and ground forces from missile or artillery attack.