-Once Fahook goes into the back of the plane, he will drink from his bottle when you get him very low on life. At this time you should shoot the bottle out of his hands before he gains too much life. Doing this three or four times will destroy his bottle. Finish off his remaining life points and watch the intermission sequence.
-Use the manual aiming to shoot things so you can aim at the bottle. You will need to do this three or four times. When the bottle is shot off Fahook, you need to make Fahook go near the open back part of the airplane. Once there, shoot him and Fahook will fall off and die.