The marching-on-in-time method is employed in analyzing the ultra-wideband electromagnetic scattering problems of aircraft's basic parts (sphere, cylinder, sheet metal). A magnetic field integral equation is derived, and the result obtained is better in coincidence as compared with the measured or other computed result. The method introduced in this paper is effective, without setting the absorbing boundary conditions, and simple in computation. Its results can be used for imaging reconstruct of radar targets compared with FDTD method, and this method can also be used for solving EM scattering problems of ultra-wideband in comparison with the method used in frequency domain.