The Northrop Grumman B-2 Spirit (also known as the Stealth Bomber) is an American strategic bomber, featuring low observablestealth technology designed for penetrating dense anti-aircraft defenses; it is able to deploy both conventional and nuclear weapons. The bomber has a crew of two and can drop up to eighty 500 lb (230 kg)-class JDAM GPS-guided bombs, or sixteen 2,400 lb (1,100 kg) B83 nuclear bombs. The B-2 is the only aircraft that can carry large air-to-surface standoff weapons in a stealth configuration.

Development originally started under the “Advanced Technology Bomber” (ATB) project during the Carter administration, and its performance was one of the reasons for his cancellation of the B-1 Lancer. ATB continued during the Reagan administration, but worries about delays in its introduction led to the reinstatement of the B-1 program as well. Program costs rose throughout development. Designed and manufactured by Northrop Grumman with assistance from Boeing, the cost of each aircraft averaged US$737 million (in 1997 dollars).

Total procurement costs averaged $929 million per aircraft, which includes spare parts, equipment, retrofitting, and software support. The total program cost including development, engineering and testing, averaged $2.1 billion per aircraft in 1997.

Because of its considerable capital and operational costs, the project was controversial in the U.S. Congress and among the Joint Chiefs of Staff. The winding-down of the Cold War in the latter portion of the 1980s dramatically reduced the need for the aircraft, which was designed with the intention of penetrating Soviet airspace and attacking high-value targets. During the late 1980s and 1990s, Congress slashed initial plans to purchase 132 bombers to 21. In 2008, a B-2 was destroyed in a crash shortly after takeoff, and the crew ejected safely.

In the mid-1970s the search for a new U.S. strategic bomber to replace the Boeing B-52 Stratofortress was underway, to no avail. First the B-70 and then the B-1A were canceled after only a few of each aircraft were built. The B-70 was intended to fly above and beyond defensive interceptor aircraft, only to find these same attributes made it especially vulnerable to surface-to-air missiles(SAMs). The B-1 attempted to avoid SAMs by flying close to the ground to use terrain to mask its radar signature, only to face a new generation of interceptors with look-down/shoot-downcapabilities that could attack them from above.

By the mid-1970s, it was becoming clear that there was a different way to avoid missiles and intercepts; known today as “stealth”; the concept was to build an aircraft with an airframe that deflected or absorbed radar signals so that little was reflected back to the radar unit. An aircraft having stealth characteristics would be able to fly nearly undetected and could be attacked only by weapons and systems not relying on radar. Although such possibilities existed such as human observation, their relatively short detection range allowed most aircraft to fly undetected by defenses, especially at night.

In 1974, DARPA requested information from U.S. aviation firms about the largest radar cross-section of an aircraft that would remain effectively invisible to radars. Initially, Northrop and McDonnell Douglas were selected for further development. Lockheed had experience in this field due to developing the Lockheed A-12 and SR-71, which included a number of stealthy features, notably its canted vertical stabilizers, the use of composite materials in key locations, and the overall surface finish in radar-absorbing paint. A key improvement was the introduction of computer models used to predict the radar reflections from flat surfaces where collected data drove the design of a “faceted” aircraft. Development of the first such designs started in 1975 with “the hopeless diamond”, a model Lockheed built to test the concept.

Plans were well advanced by the summer of 1975, when DARPA started the Experimental Survivability Testbed (XST) project. Northrop and Lockheed were awarded contracts in the first round of testing. Lockheed received the sole award for the second test round in April 1976 leading to the Have Blue program.