I was speaking of the angles in the shape of the planes design.<p>Have you ever seen a diffraction pattern caused by any discontinuities?<p>I have seen thousands of them ... the fourier transform of any discrete functions makes very nice detectable pattern that says : &quot;NOT NATURAL&quot;. And that what radars are trained for spotting.<p>And the more symmetries the more the pattern reinforce itself saying: human made technology spotted. (Curie principle : symmetry in causes get propagated in the effects)<p>Have you seen a lot of natural object that are both discontinuous and symmetric and the size of a plane?<p>EDIT : I forgot to explain the relationship between convolution of signals and FT but I guess everyone is educated enough to know that convolution of signal is the base of radar detection and that Fourier transform are related to convolution.