Quinn attaches helium container to a balloon and receives flute from the Leader of the Spill Mountains people. He has to manipulate balloon's movement using altitude controls.
Best method of approach:
Take her all the way up. Move with the wind until balloon passes river and keep going for about one screen. Now take her down (as low as you can) and after a little ride Quinn should arrive at desert scene.

Get out Quinn's comscanner and move towards tha ARM base (arrow on comscanner's screen while using SCAN button). Repeat the procedure until you arrive at the forest. Quinn should move something like:
east - north - north - west - north - east

At the ghoul village try to play flute.
Go after the ghoul and talk some more. He leads Quinn to an ARM outpost. There are two different ways to take out ARM guard, one involves shooting him while the other, more delicate approach requires Quinn to strike up friendly conversation with a guard. Guard out of the way, quinn assumes his post at watchtower only to be picked up by ARM hammerhead.