Because of new Russian and Chinese Fifth Generation Fighters, which will compete with the F-22 Raptor in the Air and the F-35 Lighning II on market place, the US Air Force is searching for technologies for an aircraft with enhanced capabilities in areas such as reach, persistence, survivability, net-centricity, situational awareness, human-system integration and weapons effects.
Currently Boeing is working on concepts and studies for the F/A-XX fighter program, to develop a successor to the F/A-18E/F Hornet carrier-based aircraft.
But the problem is that Air Force Secretary Mike Donley made very clear at the Air Force Association conference that the service is focused on building the coming fifth generation aircraft (also known as the Joint Strike Fighter) and has no plans to begin investing the nation’s treasure on a new aircraft. “I don’t think you are going to see a sixth generation fighter program any time soon." “We do not have the resources available to ramp up for a sixth gen fighter. We are still working on the fifth.” But Air Force chief of staff Norton Schwartz announced: “Within the next few years, we will begin work on the sixth-generation capabilities necessary for future air dominance. Donley could argue they are still working on those capabilities. just not within the purview of a formal program structure." But Donley stated that the absence of a Sixth Generation Fighter would not be a disadvantage for the United States: “The United States is still, and as far a I can tell, the U.S. will remain the essential force for stability in international security.” 
Proposed differences to 5th Generation FightersEdit
The greatest advantage to 5th Generation fighters will be stealth, the appearance of newer detection systems and more advanced radars will require a new super stealthy aircraft shape to counter counter stealth; a much smaller Radar cross section than on current stealth aircraft like the F-22 Raptor, B-2 Spirit, and unsuccessful designs like the YF-23 Black Widow II will be also needed. A new generation of engines allowning ultra high altitude flight and supercruise speed of over Mach 2.2 as well as a new generation of armament like directed energy weapons to attack enemies with the speed of light, are planned to be included.
Their avionics will feature next generation electronic attack, passive detection, integrated self-protection and cyber attack capabilities.
In summing up sixth gen fighters are expected to outperform current 5th Gen fighters in terms of speed, range, stealth, self-healing structures.