The Northrop Grumman B-2 Spirit is a multi-role stealthy bomber able to drop conventional and nuclear weapons. The bomber was a milestone in the bomber modernization program of the United States. The B-2 is one of the most expensive planes ever built: estimates for the costs per plane range from 1.157 billion to 2.2 billion US dollars.By comparison, a Nimitz class aircraft carrier costs $4.5 billion. However, quoted cost figures are highly inflated by the inclusion of the aircraft's enormous development cost and infrastructure development costs in the unit price; published estimates have shown the unit production cost for the aircraft alone is approximately ten percent greater than the B-1B Lancer, at approximately $150 million per aircraft. Its stealth technology is intended to help the craft penetrate defenses previously impenetrable by combat aircraft. The original procurement of 135 aircraft was later reduced to 75 in the late 1980s. In his 1992 State of the Union address, President George H. W. Bush announced total B-2 production would be limited to 20 aircraft (later increased to 21 by refurbishing a test aircraft).
