A sixth-generation fighter is a conceptualized class of jet fighter aircraft design more advanced than the fifth-generation jet fighters that are currently in service and development. Several countries have announced the development of a sixth-generation aircraft program, including the United States, China, United Kingdom, India, Russia, Italy, Sweden, Japan, Germany, Spain, Taiwan and France. Currently, the United States has two projects: the Air Force's ‘Penetrating Counter-Air'—a long long-range stealth fighter to escort stealth bombers—and the Navy's FA-XX. So far, Boeing, Lockheed-Martin, and Northrop-Grumman have unveiled sixth-generation concepts.