I think you have to be at either east river plains or west river plains to do it firstly you need the airplane radio and the thing that looks like a sky TV dish then you repair the radio scroll up on...
you have to get the radio and transmitter put them together on the volcano and send sosor on the last island you have to build the last boat and sail to help
1. Find the radio and transmitter (you can find the transmitter in South River Jungle right where the plane broke in half. you need to cut down some vines before you are able to see it, though.)
2....
You have to find the radio and the transmitter and go to the Volcano Summit on the Third Island. Take the radio out of your inventory, put in down, and click on it. It should say, 'Repair'. Click on...