Photos: The blended-wing design of Boeing's X-48B

The low profile of the X-48B bears a strong resemblance to that of the B-2 stealth bomber, already in service with the U.S. Air Force. This mature 336,000-pound design (gross takeoff weight) can fly more than 6,000 nautical miles without refueling--10,000, with one refueling--pushed by four General Electric F118-GE-100 Turbofan engines, according to Northrop Grumman, the prime contractor for the plane. One B-2, out of the 21-plane fleet, is also stationed at Edwards Air Force Base, where it's used to validate upgrades to software and weapons systems.