Sure, but you can drive a TRUCK to within a few hundred feet of the capital and detonate it, and it could carry more radioactive material and more explosive to spread it then any Cessna 152, an airplane with like a 450lb useful load. Subtract the weight of the pilot, the fuel needed, and even play around with the max gross, and it's still an order of a magnitude smaller then what a truck could carry. This is in response to the 'dirty bomb' argument.
For the Milan pic, the Rockwell 112 has a max gross of 2,800lbs and cruise of 135 knots. The Cessna 152 has a max gross of 1,600 and cruise of 107knots. So the kinetic energy of the Rockwell is a little over twice that of the Cessna. No conclusions, just a point of comparison.