During the ‘90s the United States Department of Defense launched the JSF (Joint Strike Fighter) contest to assign the production of a new 5th generation Multi-role combat aircraft. Boeing participated to the contest with the concept demonstrator aircraft X-32 while Lockheed Martin presented its XF-35 prototype. The Boeing X-32 was developed and realized around a large one piece carbon fiber composite delta wing and characterized by the big size air intake placed under the cockpit. The Lockheed Martin reply was based on the XF-35, using a lot of technology and aerodynamic solutions already successfully adopted on the fighter F-22 Raptor. For both concept demonstrator aircrafts were developed several applications as the conventional take-off / landing version and the STOVL (short take-off and vertical landing) version. On 2001 the Department of Defense announced that the Lockheed Martin X-35 won the JSF competition and from it the new F-35 Lightning II was born.