WASHINGTON (Reuters) - The futuristic F-22A "Raptor" fighter jet, designed to dominate the skies well into the 21st century, joined the U.S. combat fleet on Thursday, 20 years after it was conceived to fight Soviet MiGs over Europe. The Air Force said "initial operational capability" had been achieved at the 1st Fighter Wing's 27th Fighter Squadron at Langley Air Force Base, Virginia. Pilots in the squadron, the Air Force's oldest in continuous operation, have been training on the F-22, the Air Force's most advanced weapon system, for about a year. "If we go to war tomorrow, the Raptor will go with us," Gen. Ronald Keys, head of the Air Force's Air Combat command, said in a statement. He said an initial group of 12 was ready for combat worldwide or for homeland defense. The squadron may swing through the Pacific next year, probably flying from Guam and elsewhere, though no decision has been made about where to best "showcase" it, Keys said in a later teleconference with reporters. With the Soviet union" gone, defense analysts have cast the F-22 as the weapon of choice for any future U.S. conflict with China, for instance over Taiwan. "There is a clear role for F-22 here," said Daniel Goure, a former Pentagon strategist now at the Lexington Institute, an Arlington, Virginia, research group with close ties to the U.S. defense establishment. The aircraft's role is to "kick the doors down" in a conflict, as Pentagon officials put it, knocking out defenses on the ground and in the air to clear the way for other warplanes and forces. The radar-evading Raptor is twice as reliable and three times more effective than the F-15C Eagle it is replacing as the top U.S. air-to-air fighter, according to Lockheed Martin Corp., its developer. "It's a fighter pilot's dream," said former F-15 pilot Col. Walter Givhan, lauding the plane's integrated avionics, stealth and speed. Givhan is wing commander at Nellis Air Force Base in Nevada, where the latest round of F-22 testing was completed. Lockheed described the fighter as the world's most advanced and said it was "relevant for the next 40 years." Boeing Co. and Northrop Grumman Corp. are top F-22 subcontractors. United Technologies Corp.'s Pratt & Whitney unit makes the aircraft's two engines. STEALTHY AND SUPERSONIC The Raptor combines low-observability, or stealth, with supersonic speed, agility and cockpit displays designed to boost greatly pilots' awareness of the situation around them. At a "fly-away" cost of about $130 million each for the most recent batch, not including research and development, it is also one of the most controversial U.S. warplanes ever. Critics have termed it unaffordable overkill in a world without the potential threat of a Soviet union" able to send swarms of MiGs into a dogfight, which prompted its inception in 1986. The Air Force is planning to stretch F-22 production until 2010 to keep Lockheed's production line open pending arrival of its more affordable F-35 Joint Strike Fighter family of aircraft that will also go to the Navy, the Marines and co-developing nations that include Britain, Italy and Turkey. The F-22 also has a ground attack capability to drop 250-pound (113.5-kg), small-diameter bombs or 1,000-pound (454-kg) Joint Direct Attack Munitions while flying at supersonic speeds. Gen. Michael Moseley, the Air Force chief of staff, has said the F-22 is needed against threats such as Russian-built surface-to-air missiles sold overseas. Moseley said on Tuesday he hoped to buy 183 F-22s, four more than currently in the budget and enough for seven combat-ready squadrons, down from the 750 F-22s once planned. Final assembly has been completed on 67 of the 107 F-22s already purchased by the Air Force, Lockheed's program manager, Larry Lawson, said in a statement.