How does radar not detect a B-2 stealth bomber? How can an aircraft with a 172-foot wingspan register as small as just a large bird, if anything at all? The Northrop B-2 Spirit escapes radar by being specifically designed to reflect radio waves away from the source so it’d never be detected.
But the stealth bomber has more radar dodging tricks than just reflection. The B-2 was made with the aid of a supercomputer and computational models to develop its curved shape, and the B-2's streamlined wing design and placement of the engine (embedded in the plane’s body), all add up to make it more invisible to radar. The engine’s intake and exhaust are on top of the plane to avoid being spotted by ground-based devices. Even the paint of the aircraft is special, with iron particles in it to absorb electromagnetic energy and convert it to heat.
There are a lot more fascinating tidbits on how the B-2 works in the video by Real Engineering below.