You cannot get an airplane in GTA Vice City Stories on PSP. The PSP version (and the PS2 port) does not include flyable fixed-wing aircraft.
UP, DOWN, LEFT, RIGHT, L, R, L, R, TRIANGLE, CIRCLE (enter during gameplay).CIRCLE, X, L, L, R, R, DOWN, DOWN, UP, TRIANGLE.For fixed-wing flight, play the PC/PS2/Xbox versions of GTA Vice City or San Andreas.