  This paper is concerned with the convergence rates of subsonic flows for
airfoil problem and infinite long largely-open nozzle problem, which is an
improvement of [7,11,15,20]. The maximum principle is applied to estimate the
potential function, by choosing the proper compared functions. Then, by the
weighted Schauder estimates, the convergence rates of velocity at the far field
are shown as $|x|^{-n+1}$. Furthermore, we construct the examples to show the
optimality of our convergence rates and the expansion of the incompressible
airfoil flow at infinity, indicating the higher convergence rates $|x|^{-n}$.
