  The propagation of surface plasmon polaritons in thin films of topological
insulators is studied. The materials considered are second generation three
dimensional topological insulators Bi$_2$Se$_3$, Bi$_2$Te$_3$, and
Sb$_2$Te$_3$. Dispersion relations and propagation lengths are estimated
numerically, taking into account the variation of bulk dielectric functions of
topological insulators as well as substrate using the Drude-Lorentz model. Key
factors affecting propagation length are identified and ways to modify the
dispersion relations are suggested. The explanation of the apparent discrepancy
between the experimental data for Bi$_2$Se$_3$ and theory is proposed.
