The problem of the intense femtosecond pulse with elliptical transverse distribution propagating in air is reduced to an analogous problem of a particle moving in a two-dimensional potential well using variational method. Different types of initial conditions are considered to provide direct physical insight of how the self-focusing and defocusing mechanisms can lead to long distance propagation and refocusing phenomenon. The difference between elliptical and circular transverse distribution beams is compared and discussed. The results are coincident with direct numerical simulations.