Spirit bomber

This is the now classic stealth design of the B-2 Spirit bomber. The plane keeps an extremely low profile in the air through a mix of factors, with composite materials and special coatings helping to minimize infrared, acoustic, electromagnetic, and radar signatures. Most dramatically, it uses a flying-wing design in which the fuselage seems almost absorbed into an oversize wing structure, and there is no vertical tail at all. (For a lookalike aircraft still in the prototype phase, see "Photos: The blended-wing design of Boeing's X-48B.")

It's been almost 20 years since the plane's public unveiling and first test flight. The B-2 entered service in 1997, and the Air Force now has an active inventory of 21 planes.