It depends on how much current you are drawing at full throttle. Castle Creations recommends a 5mph air flow to achieve 100amps on their new ICE 100 ESC. A small air flow is better than nothing so if you are close to 100 amps, try to mount the ESC for some air flow. You can put it in the air intake duct or near a cheater hole. If you have landing gear, cut a hole in the bottom of the plane so that the heat sink fins have some air flow on them.

Good luck!